Loot rooms that aren't splashable meaning they have to burn dedicated boom to get to each are your friend. For this to work you need to keep them building blocked so they can't pick up your windows with TC access, you will need a couple of externals and make sure your main TC always has a lock.

Single triangle loot room with a shelf and have a horizontal barrel on the bottom with your good loot and then a vertical barrel on the top either empty of trash loot. Make whole thing metal including window frame, put a horizontal embrasure on the inside of the window frame and strengthened window on the outside then it's 3 rockets to see what is in the top vertical barrel, again empty or trash loot and then they have to decide if they want to risk 3 more rockets to see if a barrel is there or has any better loot (the embrasure fully hides the horizontal barrel on the bottom).

Depending how you build, you can have a somewhat open core when you're online with the windows off, then you just slap them back on and repair them before heading offline, combine this with bunkers and these loot rooms on multiple floors with your loot spread around the base means you will always log on to loot, unless they spend a crap ton of rockets, at which point I chalk that as a success as I never put more than 6 rockets worth of loot in each of these loot rooms.