Hmm, you can recruit nobles in villages connected to castles especially... and you can also use the Leadership perk and turn forest bandits into battanian nobles. I know you know this.
Other than that, I just played as vassal for Battania and I found defeating vlandians pretty easy... Battanian infantry is pretty beast, and seeing as I played almost full party of infantry it was really easy to win battles by just rushing in with a shield wall. Of course if you're trying to have a long range warfare nothing will beat the beast crossbows.
The only reason I might agree with the fact that the wildling tree could be turned into archer units instead is because the oathsworn and wildling are such similar units atm. They both have same equipment, including the same shield. Ever since the oathsworn's shield has been changed to the exact same one as the wildling's I feel like the lack of distinction between the 2 units just makes one or the other useless to have in the game.
I've had the exact opposite problem, in that my infantry was just getting cut down before I could do anything about it. It forced me to adopt a new role though, in that I became a hunter killer on the battlefield. Light crossbow with the sheriff perk, not much could survive the head shot so I went about hunting high value targets on the field. But still, my units were just getting done in by the combined might of Vlandian shock cav and the crossbowmen.
I know to use cover and all but there have been plenty of times where the enemy won't march forward because they are on the defense and I have to move my units up under a hail of bolts. Just having a basic archer class I think would be more lore consistent and beneficial to the Battanians.
Also I wasn't around for the old Oathsworn or anything. I picked up Warband like two months ago, and jumped into Bannerlord not too long ago.