If they are 3 and 4 ways, can you put the dimmers in other locations? Possibly lutron maestros which give you dimming control at all switch locations. The ones at the door would be the lutron maestro accessory dimmers which are just controllers, the dimming is done at the main dimmer. I'm not sure if the accessory dimmers are any smaller than regular dimmer switches though. It also seems the new lutron toggle type dimmers are a lot shallower than other dimmers, plus they have screw terminals eliminating extra wire nut pig tail connections in the box.

If you can live with the looks you could always add a wiremold extension box to your present one. That should give you the depth that you need.

The first of the receptacle-type GFCI's were often too deep for existing boxes. Manufacturers often packed a thick extender ring with the GFCI that fitted between the wall and the receptacle plate. I know of no place to get those as separate items at this time. I have few of them on hand, accumulated years ago. You might look at Wiremold Series 100 extender boxes. Do the legwork yourself. An Internet search for Wiremold will get you to their site.

"new boxes will not fit in the wall "

How thick is the wall?
You can try larger 4x4 boxes with a plaster ring and usually get dimmers to fit.
4x4 boxes go as shallow as 1.25 plus another 1/2 for the plaster ring gets you a box depth of 1.75 with plenty of box volume.

I'm not sure why you would need to relaminate the plaster.

If you can get the old box out without damaging the plaster then you can use a remodeling/old work box for the dimmer.

If some of the plaster is damaged you could use an oversized plate to possibly cover it up.

Earlier I mentioned a Wiremold 100 box. A web search makes it seem if the series below 500 has been discontinued. I know I have a few items in series 200 on the shelf.