Think of the Halo 2 mission “Regret” when you are in the towers over the water. Red base and Blue base will be towers, connected by gondolas up top and one underwater elevator linking the two bases at their centers.
Think of your standard symmetrical Capture the Flag match but with long range/sniper combat between bases and close ranged skirmishes on the moving gondolas and inside the bases.
(oh, and of course there will be the one player who will have a shotgun or sword in the elevator because that’s just how people are online)
All the while the map will be extremely beautiful as it would bear resemblance to Delta Halo, the architecture was amazing, the underwater elevator scenes were, for it’s time, breath-taking, imagine that with updated Halo 4 style visuals.