Once you are converted all you can really do is use turns to sell.

Would it be insane to have some kind of option (like e.g. cashing, or teching) but based on MB's that effectively grows your private market in some way.

The cost of running turns would give it some nuance, like you cant just spam all your turns once you convert, but correctly balanced this mechanic could have you attempting to balance the cost of running turns against the potential benefit of reselling additional military.

If might create an interesting dynamic towards the end of the set, because this is historically a time where the public market empties due to supply and demand issues, buffing MBR generation might mitigate the supply shortage somewhat.

The main downside I can think of, is that it would potentially nerf some of CI's endgame potential.

(That also makes me wonder about some kind of "working overtime" use of turns for CI, and maybe even farmer? this could be a nightmare from a game balance perspective, but also make destocking for farmer a little less banal than just keep grabbing)

Public market will empty sooner or later. Having a bigger PM just means players will jump later, but milt prices will still peak.