I wouldn't say that an X7classic is excessively complex. It does have a bit of milsim goodness (or badness? depending on your viewpoint) tacked onto the outside making it a little funky to break open... but once you're inside, its an inline blowback.
I love tippmanns (and their clones...) for their simplicity and durability. I've never bought one home that I couldn't get working with little more than some oil and o-rings (and I've brought home some pretty gnarly looking garage sale tippmanns)