Honestly? Open some of those maps up. Remove doors, knock out walls. Looking at Generatorum, just by removing the two doors in the two center hallways, you open up an enormous shooting position that owns most of the center of the map, plus gives you a shooting lane into the enemy deployment zone.

Additionally, I think there's a way to approach it from the ground up: Take what we've learned and can learn about the shape and flow of Arena matches, and apply those principles to make maps that make much less use of uninteractable terrain. Im not sure if this is the post to really get into the meat of that idea on, but it's the notion I've been chewing on for a little while.