This concern has probably been taken up before this post. I have been playing this game quiet long time now and seen how it has been advancing forward. One of the biggest concerns for me is the combat system and unit losses. While the combat system is very different than in other games, and thus unique and fun, I am still concerned about the future of it. The problem is that i see various unit types becoming "useless" as most of the server population starts to advance into endgame. The combat tactics often involve around same kind of unit combinations, while taking losses to recruits, militia while rest of the general unit room is saved for heaviest damage dealing units and cavalry is only used when no first strike units are present on opposing side.
Most of the endgame adventures only need losses in recruits, militia and sometimes cavalry ( losses on rest of unit types are very rare). While in growing server all units are needed as player base levels up, in the endgame some of them come obsolete. This can be best seen in drop of cost of longbows, bows (and over the time it will also happen to xbows, cannons and dam. swords).
Who would take losses example on Xbows or cannons if you can loose militia / recruits instead ? No one sane at least. Accidents do happen and sometimes expensive units might be lost, especially when playing around blocks, but people tend to learn from mistakes. Thus the amount of those type of units needed are limited.
I really hope that BB will add some continuous need for ranged unit types + elite soldiers, so they are needed in the future as well.
There is few adventure out there like motherly love and horseback, where different unit losses can be used than in generally. I hope more of those are added.