[joe0888]

The house is 35 years old. When I tried to install some new specialized switches in the bathroom, there was not enough room in the box for the wiring behind the new (larger) switches. Is there any solution other than cutting the drywall, removing the old box, installing a new larger box, and then patching the drywall. (The wallpaper is new and perfect.)

[Nwptsailor]

There is such thing as a surface mount box, which could be installed over the existing box. Some have a relatively low profile. The white vinyl ones look pretty good in some applications.
Another possible solution is to ( very carefully ) drill out the rear of the existing electrical box . Keeping in mind that the whole idea of a box is to surround all wire terminations so that a spark cannot infiltrate the wall.
If great care was taken to deepen the box and all connections were very well taped , you may be able to make it work.

[labman]

Another possible solution is to ( very carefully ) drill out the rear of the existing electrical box .

I think that would violate code. Wait until you hear from tkrussel before doing it.

[tkrussell]

The box sailor is talking about is a WireMold extension box, they make them for two gang boxes and can add about 3/4" of depth top the flush box. The come in white, and in metal and plastic.

The idea of cutting the back of the box to add depth is just not allowed.