My understanding: it is all about game theory, and the solution for UASF having minority hashpower has no stable Nash equilibrium, but multiple equlibria (“local optimums”). We may face multiple “phase transitions” between those unstable (horse-seat) equilibria which you describe as “reorgs” or “chainsplits”, but they are mich more dangerous than usual reorgs and even chainsplits.
This means that the main problem that the consequence of BIP-110 will be turbulent and uncomputible; chaotic, whether tiny unpredictable events may have a dramatic impact.
If I am right, even if nothing happens and everyone will forget BIP-110, we have explored a profound vulnerability and attack vector agaist bitcoin (actually any PoW consensus based on a public ledger) which will be used in the future, including government-based actors.
Here, non-blockchain PoW like I am planning for Prime is the only solution to the fundamental problem.