In a 65g it would be possible to have a red and green BTA IMO, but just be aware that might absorb all space in that tank and make it tough to have any corals, or at least corals other than say zenia or something that can handle their sting.
As for damsels accepting host from them is hit or miss.
It took years before my chromis finally went into my nems, and I was sure they were about to become nem snacks when they did.
I do think certain damsels can at least adapt to them, or at least deal w/ stings, but not sure what species that would all be included in being able to do this.