I get such a kick out of the router love on this site LOL!!!!
I wouldn't route it off, that wouldn't even be my 3rd choice.
First choice would be a bandsaw. But it has to be the RIGHT bandsaw, I'm not talking a little 14" with a 1/2" blade (although I'm sure you could do it with that too) but a LARGE bandsaw with like a 1.5" resaw blade. Set the body up against a TALL rip fence, cut the top off leaving 1/8" and then run it through a thickness sander.
Second choice would be to run it through a thickness sander with coarse belts until you were nearly done, then smooth it out with a finer belt. I would not use a thickness planer for this job due to all the routes in the wood and the fact that figured wood really doesn't work well in a planer.
Third choice would be to steam the top off, I've seen this done on a LP and although it's not my first choice, it saves the top and the back of the guitar. Yes, it's very possible and is the only non-destructive method of removing a top.
Maybe for a fourth choice I would route it off, but man, this means you need a HUGE router base, and a level jig all the way around the entire body, plus a way to secure the jig and body all together, yeah, it's not hard to do, but in the time it takes to build the jig and router base you could have bandsawed it off or thickness sanded it off.
Routers have their place, IMO this would not be one of those places.
Just my 2 cents.