Shower/Bathroom remodel...advice sought

Background: Recently purchased a house that was built in the late ‘60’s (Corpus Christi, TX…i.e. gulf coast, hot/humid/termite heaven).

The upstairs shower began leaking through into the laundry room below. After removing the damp drywall from the laundry room ceiling the rotten plywood of the upstairs bathroom was partially visible. I finished removing the tile (3/4 of the bathroom walls were tiled along with the shower) today and found interesting (and depressing) stuff.
1. The frame/studs for the shower surround are severely termite damaged
2. The shower floor had no pan. The tile was laid on aprox 4” of cement/grout which was poured on some type of ‘tar paper’ which was on top of plywood.
3. The plywood appears to have been both termite damaged and rotten from the leaking shower.

Questions:
Was is ‘normal’ to not have a shower ‘pan’? I’ve always seen older houses with iron pans that eventually rust out.
If it were you (looking for opinions here), would you: re-tile, put in a fiberglass surround, or ?
We will likely be in this house for 3-5 years as my wife is in the Coast Guard and we’ll be moving on down the road eventually.
I can post pics of the damage once I remove all the tile debris from the bathroom…I’m off to remove the linoleum floor in the rest of the bathroom to find out how extensive the rot is and to check the support beams.

Cheers,
Russel