I already considered that after her last accident. The body shop said to find another shop since they were tired of working on her car. The hospital said, "Just send us more money". The insurance company said, "Start looking for another insurance company."
We installed Hickory on the first floor, and I am thinking that something else would be nice for the second floor. There is no problem with transitions on the second floor. Presently there is 3/4" plywood under the carpet, and I want to remove that and put the boards that are cut for radiant heat in place of the plywood. There are two large bedrooms and two baths, so it will be too large of a project for me to tackle. Besides I am more of a framing/rough carpenter than a finish carpenter.
I'm a huge hickory fan, we don't get a lot of anything hickory here in the PNW, almost everyone wants to go with Alder for cabinets and Bamboo or knotty Pine for the floors.
I have huge butcher block slabs of hickory that will hopefully become my kitchen island this year.
Go with engineered and not solid, it handles temp and humidity swings way better.
And yes most good flooring will be pre finished.
For the radiant heat, get good thermostats / controllers for it, makes the world of difference in the performance and feel.er
Our entire house is Hydronics heat, love it!
Our floors are HVLP because we get better conductivity for the heat, and it's wear / waterproof, and with as many dogs, wolves, and cats as we have running around that was real important!