[Alternative Ideas]

A scaled proxy mine limit, for example first 10 players : 30, and for every x players after that y mines, with perhaps a maximum (say 50).

The idea came to me after having played hardcore marathons in the original, in c&c_hourglass with 127 mine limit. Raising this limit made the team effort really pay off!

[The end game is really weak]

A third option would be to make a 'last stand'- mode, which doubles the points gained, and unless the base is completely destroyed the team with the most points would win after X minutes.