It would be awesome to have the ability to custom create the map -- as in specify what blocks are where, and what access level that they have. The idea I was thinking of is that there is one combat I remember (*only one*) in Pool of Radiance, iirc; which you fight the enemy in a wilderness combat map with a river between you and them. You crossing the river greatly reduces your movement while in the river, but it is passable.
I was thinking of things like the above. We currently do not even use the river graphics, nor did FRUA. But that was obviously something that they had on the todo list or something that was "in the works" to use.
My ideas for taking this further, define areas of the combat map which would do the following:
allow no movement, but would allow ranged weapon and targeted spells to pass thru -- something like an arrowslit (https://en.wikipedia.org/wiki/Arrowslit
allow cover from ranged (areas which would make penalties to ranged attacks coming in, such as hiding behind a tree, overturned table)
reduce stats temporarily such as movement rate, or AC (can't properly defend if you are ducking under low ceiling)
Just some ideas that would be awesome for future expansion
ST the expanding