as said, not enough meat between the bores to gain that much. you can go to 84mm ok, you could physically go a lil bit more but you risk losses due to bore flex and gasket sealing issues.
as for increasing stroke, these engines are massively under-square by comparison to other manufacturers well-spec'd 2.0's, so whilst yes it could be done at cost, there is an eliment of detriment. especially if you plan on making power at higher revs. cost wise, a crank would cost about £2k, and then custom pistons to reduce the deck height £600. you could have shorter rods made, but then you really are making the rod-length/stroke ratio too low, where its already really very low as std.