Hopefully their assessment and/or restoration work will keep C/E satisfied.The flood was from the bath tub not toilet.

In my opinion, allowing them to stay during the process is not a good idea.There will be no kitchen sink usage (drain will be cut off).The toilet may be removed to allow room to operate.The wall above the bath tub will be opened with tiles removed (no shower).There will be carpenters, plumbers, myself, helpers, coming in and out.We may run into some unforseen situations that may require plan B, plan C scenerios.She has two cats. 

As long as the hump (like the side of a bathtub) is lower than the top of the tank (maybe six inches below the top of the unit itself), siphon action will pull the last of the water out.How often do I do it?

I don't expect to see a large high end shower that no other house has and makes me say I could easily do without a bath tub in my Master because I have this awesome shower. 

Then there are the units from Home Depot and Lowes that cost around $200 and install the pump at the hot water heater (still need a GFCI there but probably easier to put there), and the mixer gets installed at the fixture (sink or bathtub).

Is there any way I can save this bathtub?

We had to slide the bathtub out of the way and cut open the very same drywall that I recently had hung.

(But there are weeks like the one I'm having:  Current tenant overflowed the upstairs bathtub. 

However, they left some rust stains in the corner of the bathtub (what looks like from a metal can they had there), I've tried CLR, Lime away, bleach, etc. and I cannot get this to come out. 

Also - never paint bath tubs.