IMO AI placement games is theoretically not a problem:
Assume:
- We have infinite AIs for every level of play, none cheat
- These AIs are absolutely accurately gauged based on the current skill distribution
- There are no reasons to expect large shocks in player distribution, similar to when FAF saw large growth after 2019
Then the interpolation can simply scale you by putting you against AI rather than players at various levels. If you lose a game, you default to the rating of the previous AI you faced for example. It would rise by 200, resulting in 10 games max for someone that was at a 2000 skill level.
This means no players are bothered by facing people during placement matches. You could also simply start at a higher rating if you want to lower the amount of placement games for the upper tier of FAF.
However, these assumptions are quite far from what are current FAF resources. So instead, a review of what is available needs to be done which can then guide further implementation decisions.