I would at least flip the sauna and steam room 90 degrees and put them against the wall. Then, move the washroom/lockers door closer to the stairs and open up the stairs a bit(instead of having a wall where the steam room is). Something still seems odd about this layout. I think it is because the stairs are breaking all the spaces up from each other? If I was doing a sports court and workout room in the basement, I like the idea of the workout room overlooking the court. The stairs between the 2 of yours really break that up. I would also want to be able to lounge by the endless pool and have kids play in it. You have very little space around your pool, which makes it feel very utilitarian. Overall, I would personally want the spaces more connected.

Scratching comes from movement. Denting comes from DROPPING something. Since the machine will be PLACED on the floor (no one is going to drop it from an upstairs balcony). Staining is something you may have to deal with. You may not. Yes the feet may have rubber on them...but the small amount is fine. If it does stain a little bit, you can be content in the knowledge that you can always hide it with an area rug AFTER the work out machines are gone. Trust me when I say this, rugs and mats and rubber stuff can cause WAY more problems to a hardwood floor that 4 rubberized feet (per machine). If you really are worried then remove the hardwood (nope, not kidding) and store it. Then install some cheap cork flooring in there and go for the works you want. When you are done with your fitness studio, you remove the cork flooring and reinstall the hardwood. There. No harm no foul. But you don't NEED to do anything but put the machines down and live your life. Wood is AWESOME at being a floor. That's why the world has been doing it for 10,000 years (probably more...but historical records are hard to find on the subject).

A floating cork floor (click together) has a life span of 25+ years. As for durability of the cork itself, the US Library of Congress has had their cork floor (same stuff minus a few repairs) since the 1890's (more than 120 years). As far as we can tell (cork has only be used as a flooring material for 180 years...unlike stone = 10,000 years of use) cork will last as long as the thing it is glued to lasts. It is like rubber. So long as the adhesive keeps on keeping on the cork will too. That should be long enough for a work out space.

We got our basement gym flooring from Costco. It is a black rubbery and foam-like material that comes in 2 ft by 2 ft squares. The squares fit together like puzzle pieces. It was very inexpensive. $15-20 for a package and I think each package was 8 squares. We intended this floor to be a temporary fix because the floor we planned to order from ProSource was back-ordered. However, we like it so much we've kept it for 3 or 4 years now. I have seen it at Costco a few times. I think it is a seasonal item for the New Year's Resolution crowd.