I think islands, wide spread islands, with loads of water and air vehicles
Guessing you played on Glass's fortwars?
I do really enjoy forced separation by water, but how people can still build in it.
I also didn't like how spread out Glass's updates map was. I found it hard to find people, especially as I only really played on the weekends.
I would suggest (if no islands), having some hills, a mountain or two, and also plenty of flat space for vehie battles. Provide both snipable spots up high, but also areas where people will have to go close quarters if they go there, maybe a ravine or two?