You make many good points. I especially like your thoughts on fuel supply, restrictive bridges, capture of terrain and tank recovery. Perhaps some combination of these. Requiring the winning team to simultaneously control by occupation several different locations would force them to keep several vehicles alive at the end. Having designated recovery depots for each team, that knocked out vehicles must be returned to before they can be put back into play. Using team tanks to drag knocked out vehicles to the recovery areas (might as well give those tow cables a workout) would probably work better than flatbeds. Since most model tanks dont have a neutral gear some kind of free rolling, tracked, towable substitutes might replace the knocked out vehicle, which would be hand carried to the recovery area to await getting back in the game. This would save wear and tear on the players nicely detailed model too.
Assuming your observation that discussion such as this hasn't been taking place for a while, perhaps it is time for some brain storming. It is always nice to see what others are thinking.