Replace tub surround without tearing entire bathroom apart?

Hi all:
Id like to tear out and replace the existing tub surround without tearing out all the sheetrock in the room. Ive come up with a plan (scheme?) to do this but Id like to run it past you guys to see if itll work.
The tub surround is greenboard and the rest of the bathroom is standard wallboard. The tile of the tub surround extends past the sliding shower door frame by about 4 inches both horizontally and vertically; wallpaper covers the rest of the wall, including above the tub, above the tile.
The sliding glass door frame is screwed into studs on both sides, so the edge of the tile extending horizontally past the frame is about 5 6 away from that stud and about 10 11 away from the next stud over.
What Im thinking of doing is removing the sliding glass door, then carefully cutting the wallboard/greenboard about 1/4 away from the vertical and horizontal edges of the tile. It would be tedious to cut all the way through the wallboard/greenboard this way, and use a lot of utility blades, but Im sure it can be done, leaving a clean edge all the way around. Id then tear off the tile/greenboard around the tub.
After the destruction of the surround Id then rip out 2 wide strips of 1/2 plywood and affix these strips to the backside of the wallboard/greenboard that surrounds the empty hole with a 1 reveal, using construction adhesive. The plywood reveal would give me something to screw into when I cover the wall with concrete back board. Id leave about a 1/8 gap between the concrete backer board and wallboard/greenboard and fill the gap with silicone. Id then re- tile the surround having the edge of the tiles overlap onto the wallpapered area by a very small amount, like 1/8 1/4 resulting in a good-looking edge.
Will this work? Or, is there a better way?
Tom Young
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