In this idea, both teams start out on some kind of symmetrical map with identical structures of some kind. Each team then has to try and attack the other team and level their structure, while protecting their own. Teams are also allowed to build onto their own structure in any way, while not being able to grief it (presumably all team-placed blocks would be protected, and the structure as well). The team whose structure is the last standing wins.
Any thoughts or ideas on how to improve? Personally I want this, as I feel nobody really builds anymore, and I'd like to see that change.