Patched in? No. That implies taking the same ones from Perfect Patio and putting them in base game. Now, if there were different types of hot tubs brought into base game (like ones that are built into the ground like a shallow pool with jets etc) then maybe.
The functionality isn't game-changing but it IS the main draw of an existing stuff pack. It's not on the level of, say, laundry or the butler, but it's still gameplay. And a stuff pack isn't that expensive, so anyone who really wants hot tubs should be able to get it.
(fwiw, I don't have the pack yet)
