It would be nice to have some more variety in labs, though. Once you’ve explored one or two labs, you pretty much figure out how to deal with all labs, and it becomes very easy to loot down everything. Much easier than raiding a city with a large spawn rate.
Just a random idea, but how about a lab that sort of fits in with a theme of certain mutagen. For example, plant mutagen labs have some sort of underground garden, where you can find some seeds and whatnot, and have a more forest-like area, or some sort of greenhouse. Maybe some triffids, or some type of plant monster. Or a fish/cephalopod lab, where some areas are flooded with water and you have to actually rely on the swimming skill. A slime lab where the entire place is pretty much covered in blob; walls are coated, some doors are slimed and you might have to find a way to pry the blobbed doors open, and blob type enemies to fight.
And some more generic-type labs. Like a lab that’s been somewhat bombed. Lots of wrecked rooms, some walls are broken down so there’s more open space… like containment areas so the things inside are roaming more freely in the labs, or due to some walls being destroyed there would be less cover to protect you from turrets, that sort of thing. Some areas could be radioactive, and maybe the radioactive areas have caused some side-effects with the denizens of the lab.