How about updating the elim bonus to allow it to increase over time.  It might make sense for an elim bonus of 10 units in the first x turns, but later in the game, with high army counts, it wouldn't be a worthwhile incentive.

It might make sense to have the bonus updated every x turns, similar to the fatigue factor in simulplay (although that works in the opposite direction).

Yeah!  I think I suggested something like this years ago.  My suggestion was to be able to also give cards as an elimination bonus.  It's not as flexible, but I thought it was simple and elegant, and most of the time would work ok - since for most maps cards scale as you play, and ones that don't wouldn't usually need increasing elimination bonus either.

Cards as elim bonus works nice on boards with increasing scales. Could also link it to cards less directly maybe? Elimination gives (x times) whatever the next card set gives? Proper x to be decided separately on different boards.

That works too.  With cards you could do it like you do starting cards, so you could give someone a full set of cards, or just one card, or just 1 wild card, or 3 wild cards, etc.

Good idea, but not very high on my list of proposed designer features.