Are there any other considerations to ensure appropriate liability protection in this arrangement? 

., they are going to get the accurate, honest review that they earned, not some lame response like, "We're sorry that you felt like checking in one night early, was not appropriate". 

There's a very good chance the issue(s) you face have already been discussed and answered.Ask questions in the appropriate forum.

I suppose we would and should pay as appropriate.

Airbnb offers a semd message to host option, but I'm unsure if it's appropriate to use for this purpose.

I am willing to go so far as to say they intentionally are seeking investment sources who don't have the means or sophistication to conduct appropriate diligence.Sadly social media has made it far easier for these bad actor capital raisers to get in front of their target audience with ease.

Easy to understand, hard to find someone who can structure the policy appropriately...

Meanwhile they aren't even properly prepared because  their focus is solely on forming Wyoming LLC's  but lacked the appropriate types of insurance, operate with unlicensed and uninsured vendors, never sign contracts etc.

This is different than merely being a certificate holder and have appropriate insurance (builders risk and general liability). 

I'd been searching on and off for almost a year to find appropriate insurance for my Tahoe STR.