One thing that I think would be fun is allowing units to get a slight increase in stats as a result of smart play.  A unit that destroys 2x its construction cost in enemy units could get an increase in armor, or something, reflecting the improved battle awareness of troops with combat experience.  I realize it'd probably be a chore to code, and would increase load on the servers, but still, something to think about

Trivial to write but difficult for players to manage.  Consider, if each unit type has a basic and a veteran state from the players perspective you have just doubled the number of unit types.

without some kind of unit cap or upkeep. It will unbalance the game.

Wesnoth has unit XP and levelling.  The levelling has a very low cap, usually just L1 (start), L2 and L3.  It isn't hard to wrap one's mind around the upper-level units in that game.  I'm not necessarily suggesting we do the same with Weewar, though.  It doesn't seem necessary for the time being.

Yeah, something like a one-time half a point of extra armor was all I was imagining.  It'd make veteran units a little tougher, but I don't expect it'd change any of the basic matchups.

I could go for beta testing a +1 on one or more stats, though.

I like this idea a lot. It'll keep the game from getting stale.

ha, then they could get all old and grisly looking - i keep seeing heavy troopers with cigars in their mouth

One of the reason why this game is great is because it has a good alchemy between efficiency and simplicity.

Im against adding too many complex feats like XP cause it would denature that balance that has found weewar.

Keep it simple!

I don't know, doesn't seem all that complicated. If it bothers people, make it an optional rule during game creation.

+1 for experience and veteran units! Also what's cool is that experience is diluted! So if you have an 'experienced' units that gets damage, the 'repair' will dilute it back.

Wesnoth was awesome for levelling. Very simple too.