Here is what I decided on board-wise. A fully enclosed hexagon allows up to 6 attackers to one target which is good for taking down big guys. It makes for good radial effects and it is still possible to calculate line of sight. Also, there may be some strategy to occupying the corner squares (or trapping someone there).
This is just a quick mockup that shows different "terrain" that may be traversed. With this model up to 64 resources can be on the board (not including weapons, equipment, etc) and each player can only have a total of 60 resources total to pool from so there should be plenty of room.
And with a little work on the graphical presentation, I think it can look far more interesting than a collection of squares.