The walk in tub we installed for a client last year had a double drain system that emptied the water insanely fast. No issues with getting cold while waiting for it to drain. Certainly wasn’t cheap though. Curbless shower with seat and plenty of grab bars is what’s going into my house. I can do that a fair bit cheaper and the shower uses less water as well. Not that water is an issue here in north west Canada, but still have to heat it.
