I like the initial "Oh yea!" of the basin (2 x 4 and plywood). It would indeed catch a lot of water, and you could probably arrange a drain to get the water outside safely.
However, it does not breath under the plywood, so if water ever got under there it would stay. It would mold, deform the wood, ruin the finish...
I prefer the ideas above for making as little floor coverage as possible, and moveable (sliders) at that. ]
I see the OP point, too. I also have 125 gallon tank, 20 gallon sump on newly finished 60 year old real oak hardwood floor. Also a 72 gallon bowfront with a 20 gallon sump over the same floor.
Both of the stands are DIY, and have feet the full length of the tanks.
I glued felt under the stands. I was of 2 minds while I was doing it.
a) Will hold moisture, wick it in, but it would also evaporate right back out.
b) Felt against the hardwood would protect it from getting scarred.
Point a) was a wash (pun intended!) Felt might help the water get in, but would just as easily let it back out. Point b) became the deciding factor.