Please don't take this the wrong way, but why don't you stop trying to get out of doing it the right way (removing engine) and just do it!
Its honestly not as bad as you're thinking, I guarentee you you'll spend more time worrying about it or trying to take the easy way out than you would if you'd just do it right.
As for rebuilding or just cleaning, you won't really know till you get it apart to inspect the damage. If the crank is messed up, it'll need to be machined, if not you might be able to just clean it up and put it back t/g. Either way I'd still have it hot tanked if their was metal shavings in it.
Yep its slow.
Making the world a warmer place one gallon at a time.