The MV-22 already has a take-off footprint as large as a CH-53E... making the aircraft the size of one would make the T/O footprint so large it would severly degrade deck ops on an LHD... and make operating from a Whidbey Island class LSD nearly impossible. A San Antonio LPD... yes, but only one vs the 2 they can now operate.
The MV-22 is the size it is in order to allow it to fly from the ships the USMC needs it to fly from, in the numbers they need... something your "should be" version couldn't.
There have been proposals for a larger tilt-rotor (using 4 of the MV-22 engine/rotors on two wings), with a CH-53K-like cargo and troop capacity... I believe this should be pursued, but they could only visit LHDs... not be normally operated from them.