Every Legendary creature can be used as a companion. Two Rochester picks of 16 before cracking packs. We keep that seating going into draft. The 16 are random 5 wedges/shards, random 5 guilds, one of each color, and either Bosh or Jodah at random.
Then a chaos draft.

32 total
10 Wedge/Shards
10 Dual
2 of each monocolor (10)
2 my discretion

Card choice philosophy is about half are build arounds and about half are independently good. This is more like a spectrum where everything can be built around, and everything has intrinsic value. I also tried to capture the flavor or essence of color identity in the cards I chose, to represent as many magic strategies as possible. For the purpose of identity, Alesha is Mardu.

Vannifar, Doran, and Zur are the most demanding but offer interesting angles in a chaos draft, as well as still be mostly good on their face. They have a higher ceiling if you get good support, but a lower floor without it. Should lead to some super powerful games, be challenging to draft but rewarding. Cards should be interesting enough that they are fun to play and build around but not snowball advantage as much as real companions. Every limited deck getting loaded with pre-bombs is interesting, creates a wierd format. Most don't occur immediate value, but can another cards worth of value out of it if you untap with it. There are just a few exceptions, and they basically just turn into a form of cantrip with smaller upside.

Another interesting note are my two discretionary cards. I wanted a 5 color card and a colorless card along the lines I previously mentioned. Jodah is great as a 5 color because it curves as a 4/3 flier similarly to the others, but if you untap with it and have built a 5 color manabase you can cheat an expensive spell into play. Bosh as colorless is also great. It is the most expensive of them all because it goes in every deck, a big ole trampler is fine. If you can produce red and untap with it Bosh becomes a two turn fireball. Mana intensive but has a lot of late game value, if not all of it.

The build arounds build on general chaos themes, like high toughness creatures or enchantments, that have broad applications and representation in packs. Minor overlap is encouraged, major overlaps not as much. This creates diversity, but also synergy between the first and second pick, which should help the draft identity in general. This also creates opportunity for diversity in companion drafting ideology. I also picked cards off of price (super cheap), iconicism, and chance to shine. As such many cards in this list are loved but not played. This should make for an interesting play experience and gives me the option to give them away if I want, it's about $40 for the set.

No one card should just demolish a game, and with most being clumped at 4 and up deploying them on curve should not advance a ton as most will check each other. 4-5 power, flying, vigilance, and trample are pretty common. Other keywords are limited or controlled. This should create an interesting sub-game where switching to a different companion between games would be useful. Also allowing players to use legendary creatures they find in the draft is not only fun and intuitive, but can lead to really memorable games. Most legends will either be hard to come by, won't be as useful as the more generic counterparts, or potentially one of the too good legends, which will be fun.

I see the potential for really dynamic and interesting drafts, decks, and games. It's like a step farther towards constructed without needing to balance or support. And if I give them away, these draft decks may be the seeds for EDH decks, which is fine and could result on some sweet memories.

I think I would rank them in raw power as:
1.) Keiga- When you tap out for Keiga, unlike a lot of the others, it will get full value even if it dies. 5/5 flying is also a sweet spot, and it's abusable.
2.) Jugan- Similar to Keiga but more aggressive. Triple green is why the two are not equivalent, but flying in green is powerful.
3.) Fblthp- Always means you have a 9 card hand, with potential for shenanigans. The most straight forward advantage machine. immediate value is very powerful with companion, and I believe WOTC's designs underestimated this too much. Fblthp is like a better thraben inspector every game, which is powerful, but should not be overwhelming.
4.) Artis- Similar to Fblthp but more expensive with a more useful body.
5.) Jori En- Similar to the above, but needs T4 with a one drop.
6.) Ulrich- Immediate value, and an excellent engine when you run out of gas or are ahead.
7.) Rakdos- Potential immediate value, the distance between 6 and 7 is larger. However, potentially devastating and exploitable, so the highest of these. Any of them that can answer opposing companions are the best, hence Keiga.
8.) Sidisi- Likely to hit in a deck it's featured in with recurring value and synergy over time.
9.) Temmet- Potential for immediate value, and the embalm option means you have value even after it dies. Also one of the best early play companions.
10.) Pia Nalaar- Immediate value, but weaker than the others. Gives options to the aggressive decks it will be featured in.
11-12.) Kess and Kyakar- Either with patience will act like a more expensive lurrus, requires more build around though.

Alpha.) Ascendant Evincar- Huge delta between these and above. The turn this comes down can have a huge impact on the board, but the advantage can be easily disrupted. There is an interesting sub-game with this, like Rakdos and others, where your opponent has to try not to play into your companion.
Beta.) Neheb- The best of the rest. All others require you untapping with it or connecting to gain value. The reason Neheb stands out is raw stats. Super good on the vanilla test, trading trash for treasure with mana is always good as well as exploitable, and your often happy to suicide just to get the effect. Trample here means a lot more than the others. Also, in any aggressive deck, this as a curve topper outside your maindeck is straight bananas, but not as innocuous as zurgo bellstriker would be.

Honorable mentions: Doran, Darien, and Kwende. If the draft treats you favorably, both Doran and Kwende can have huge immediate value, but would have the Evincar issue. Similar, some board states will make Darien very powerful the turn it comes down, but also can be mitigated with removal.

Initial reads on the draft environment:

General chaos rules apply. Of course the build arounds will heavily affect the draft environment. There are some universals though. Everyone will need to prioritize removal over threats, as everyone is threat laden and trying to build engines, and the relative parity will mean a lot of clogged boards. 4-5 toughness removal is strong, as well as plummet effects. Deathtouch is worth more than usual, as are combat tricks and protection effects. This is also true for creature recursion effects.

Only dragons, demons, and bosh are 6 or more power toughness, these will be stalemate breakers, even though most appear clunkier. With the curve of companions between 4-6 generally, higher costed threats will likely wheel, and cards lower on the curve will evaporate more quickly. The early game will be more significant than a typical draft. A smart player will also still pick up a few curve toppers for in the deck, as a lot of games may come down to plays their companion first or has a follow up threat. Threats larger than 6/6 should go over the top of any companion out of context.

Fixing always goes highly in chaos, but this will be even more so as folks have pre-set mana requirements they are trying to meet. Ramp is going to be stronger and more important than usual as well, especially artifact ramp. Manalith variants are likely pretty good.

Legendary or historic matters cards, or cards that have requirements of the kind of permanents you have, are more expolitable as you have more control over having a specific permanent each game.

An interesting side effect is the specialization that will occur. Folks will be very focused on maximizing their companion, and having established drafting lanes publicly before the packs were opened, should make for less competition and hate drafting. There will also be cards that will stick out for your companion that others will evaluate lower, this will be the case across the draft. Thus the omen of the sea the sidisi player passed the zur player will rejoice in, for example. This should create some interesting opportunities and draft decisions.