Nolio good brainstorming, we def need more of this.
The thing I foresee being a problem with reduced upkeep is that the returning troops blow up economy and cause abandonment - then players will be up in arms screaming "this doesn't even make sense, why are solders going to war being paid less, it's not fair!".
Plus, it's one of the canon elements of old Thardferr. It's harmless enough, so I think should be alright to stay. I'd rather buff all resource production or maybe something else to encourage war.
I thought (as I've said 100 times now) casualty caps were the ticket back in week 1 of the first test round, but I don't know if I even think I support THAT idea anymore... Theres gotta be something else better. Make resources more abundant, or make production faster, or make things cheaper - idk.
We need more brainstorming to develop a solution.