Ok, doing some critical thinking in real time here so sorry if this post ends up long or wandering:
Let's eliminate the parks that are leased land or at risk with CGA and SFDK. And take out the ones operated by Enchanted as well with WoF,
SFStL MAA, TGE, VF, Mich Adv.
I think any form of lease back takes out La Ronde and SFMexico. I'll also toss in Qiddiya City in this even though it's basically a name leasing.
Next I want to take out the ones with an RMC already with SFoT, SFNE, SFGAmer, SFFT, KD, CP.
Next, I want to take out KBF because of space limitations.
Next I want to eliminate the "is the juice worth the squeeze" ones (aka is the value there to the park) in Dorney Park (height restrictions), Frontier City (OKC market), SFDL (although I
really like this destination), and I'm adding Canada's Wonderland (potential tariff issues).
So that leaves the 3 I can make a good case for but also why not:
Kings Island - KI could really use a RMC, and is sort of a flagship for the new SF. Would be a great move for them to add for a lowered cost a great coaster to round out their collection. But the downside is with CP close enough and SV close enough, would they want both of those world class RMC's that geographically close together.
Carowinds - Like KI it could really use an RMC, it's also a flagship for the new SF, but in addition it has the already prepped spaces it could go into. The case for why not - Carowinds is a flagship park, so wouldn't you want to build them something new ground up for a RMC that would be really unique and custom to the park for the first coaster since Copperhead.
Six Flags Over Georgia - It's literally
right there and it could really use an RMC. For a park in the decline, having a world class coaster there would really make a difference. The downside here is that the attendance has been declining, Atlanta isn't a major park to get to, and there would need to be some work.
That leaves me the dark horse park that hasn't been mentioned:
SIX FLAGS MAGIC MOUNTAIN
Needs a new coaster/goodwill

Has an RMC

Has the space

Could use new signature ride

Needs investment without high expense
While it does fail the RMC already test, there's a lot of upsides to putting AF1 here. They could use a working from day 1 signature ride that's world class that won't break the bank. Especially if SFCorp decides that X2 is more problematic than it's worth. They have a lot of places it could go with minimal ride modification. And putting the #7 coaster in this park could really give it the anchor it needs to establish (deeper and more recognizably) the West Coast coaster capital that they lack.