Water is now so hot they must be having a steam bath inside the bathroom & I found that the chrome coated shower rod started to rust from so much residual water vapor.

I use a vapor oxidizing system for MH's and rentals to remove smoke smells. 

Plumber recently went down to crawl space to inspect and told resident there needs to be a vapor barrier.

Hello BiggerPockets Community,I'm embarking on an exciting journey to acquire and renovate a duplex from 1900, aiming to tackle the inherent challenges of outdated insulation and the lack of modern vapor and air barriers.

This ^^^ Or just build the little wall and stand it up in place...attach to ceiling and floor, apply vapor barrier and then cement board.

Also need one for retiling bathroom (vapor barrier and cement board).

Hopefully the crawlspace will air out, if not maybe a plastic vapor barrier over the soil will help.Good luck!

I would recommend an underpayment with vapor barrier just to give it a little bounce. 

Have them quote shingles, tarpaper, vapor barrier, flashing and any valley, material,  etc.  

I also don't see any vapor barrier in your detail.