Probably the most difficult but definitely the damage model...I was REALLY disappointed to see it's basically arcade type. Also and clearly the physics...nothing like travelling for 20 mins only to get arma'd.
Cool things to keep other team members busy (lol) tank interior.
Love the suggestions for tank repair stuff on tank itself. Super easy to implement I'd guess. But have so I may have to jump out and repair a track or something.
maybe a few different round types, explosive ect.
Keep up the good work...there's competition gaining ground on you guys!!