At least with tunneling agents its only because you tried to purposely design a place within your lair that could not be walked to, that's why they were tunneling. Ladders on the other hand are a constant annoyance that appear like clock-work regardless of what you do and must be delt with similarly.
Seriously? THATS why they were tunneling? you know how places I went to looking for any information on why thouse jerks randomly appearing in my power generation room?
In addition I agree with Zadey as well it'd be nice to have a concequence to the raids but since its by popular demand just make it so ladders don't spawn on easy difficulty. Of course ladders are annoying but Scynix has put together a rather large post on how to deal with them and linking rooms does seem to help. Although I still prefer to have a few unsquadded guards as bait and a bunch of traps in the hallway leading to my treasury. Anyways the point is that its half a measure of difficulty. It'd be like cutting out investigators from Evil Genius so you only generate heat from world map activities. Or maybe tourists...I could never get the hotel to work properly and keep them away from my lair. My freezer was huge because of it. So yea the ladders are Impire's tourists because they arn't "hard" but annoying.