[Edi]

The biggest problems would be Late Era games with R'lyeh and Ermor on the map. Either one of those and a large map hits the unit cap fairly fast.

If you really want to pay a massive, ridiculously large map, you should do it with a blank mod enabled, then copy-paste the No Independents mod into that. It will prevent the AI from recruiting hideous hordes of low resource indie chaff (because they all cost 9k gold, so can't be bought) except for the event spawned militias, which seriously cuts down on the number of units in the game. If you also avoid R'lyeh and Ermor in late era, you eliminate the biggest freespawn problem.