I know what you're thinking - 'but battanian fian champions are the best unit in the game' and that's true, but for early-mid game the battanian roster is just terrible. Given that the meta is basically archers>cav>inf the battanians do not have enough access to 'meta' units to make their campaign enjoyable, until you hit critical mass on fian champions and just 'haha longbow goes 'thwack'' your way to victory.

The highborn tree is great, but for a reasonable comp in bannerlord you need at least 30% of your comp to be archers, which for battania in early-mid game means strolling around endlessly looking for highborn youths.

in addition their cavalry is terrible.

in the mean time you:

1 - can't really engage in any meaningful battles against similar sized parties, as you'll get stomped by ranged/cav.

2 - can't really make any cash due to the above issue, aside from joining other armies and hoping the AI makes good campaign and tactical decisions. Not to mention the AI is often short on archers as well, so your battanian mob is going to to get stomped.

3 - often don't have the money to pay for large troop upgrades/maintenance while trying to farm fian champions.

all this together with the low mobility of an all-inf army (or mostly inf) means you'll be regularly stomped by similar-sized parties that catch you

The only real way I see to change this (unless infantry is buffed somehow) is to add archer type troops to the battanian main line. Realistically I'd like to see battania get rid of fian champions altogether and simply have the best archers on offer in the standard recruitment tree. (maybe not as good as fian champions, but at least comparable to, or better than palatine guard)

Right now the faction is way too dependent on having their noble troops. For every other faction these troops are a nice way to augment your army, rather than absolutely required as they are with battania. Fian champions are awesome, but I shouldn't need them just to make a battanian army feasible, and right now I do.