As long as your source hot line breaks at the switch then runs to the "line" in the outlet and your source neutral runs uninterrupted to the opposite "line" side of the outlet. Then just ground everything properly.
Normally your switches break the neutral line, but the GFCI would require the break on the hot line instead. So be prepared to break your water heater on the hot line as well.
Technically, code says only bathroom receptacles can be on a single dedicated circuit, but there can be any number of bathrooms in said circuit. However, an exception was added to say that a single dedicated circuit that controls a single bathroom may control more, and any additional permanent loads (fans, lights, water heater) are limited to 10A.
Edit: Also, your insurance company may consider a bathroom GFCI a "required" outlet, thus making it a code violation to 'switch' it.
Normally your switches break the neutral line, but the GFCI would require the break on the hot line instead. So be prepared to break your water heater on the hot line as well.
Technically, code says only bathroom receptacles can be on a single dedicated circuit, but there can be any number of bathrooms in said circuit. However, an exception was added to say that a single dedicated circuit that controls a single bathroom may control more, and any additional permanent loads (fans, lights, water heater) are limited to 10A.
Edit: Also, your insurance company may consider a bathroom GFCI a "required" outlet, thus making it a code violation to 'switch' it.