Give the attackers more tickets as well. Just make the matches last longer.
And I was just in a game where we were suppose to defend a bunker and all they did was get one more person outside the bunker than we had inside so we all died when they took the point and the map changed. most of the time defense looses because attacking side gets enough people inside the point but outside what your defending to cap with tanks sitting outside the defenses assessable map making them immune to infantry grenades. might as well just but an 'I give up" toggle for defense and make this a coop vs IA attack only game.