Ok, make the bridge(s) big and beefy. Require 2-1000 lb direct hits on the roadway to kill it. Or 8 direct hits from a tiger. Or 10 rockets and 1 - 500 lb. Something like that. Let it rebuild in 30 minuets. Or resupply it with M8's and airdrops and get it back up in 10. Line it with ack from heck on the river sides, and some puffy AI ack on the sides. Make all ack kill able. But respawns with the bridge. When one country owns the whole island, allow one town to be taken by c47 and or LVT by another country. Then the stage gets reset to only M8's can take the enemy town again.
Also make GV spawn points just outside of tiger gun range. Even put in some mannable 40's on the riversides or on the bridge heads.
Just throwing this out. Why not help me play with the idea? Keep it simple, 1 or 2 bridges, 2 towns and 2 airfeilds. Heck even allow PT's and LVT's to travel in from the coast up the river. Put a port on each side of the island, or GV parks that have to be taken with the M8 scenario until the map is owned by one country.