Of the options presented, "floating version of Spikes" is the best Nerf. Stealth Rock, in its current form, is the most braindead moves this side of Outrage. A single turn of setup for potentially massive payoff depending on the foe's types, which essentially no Pokemon is immune to? Yes, you may not NEED to have rocks, or a counter to them, to win, but by not using them, you are essentially handicapping yourself for no reason.
Alternatively, I'd say that having Rock (and maybe Ground and Steel) type Pokemon absorb SR on switching in would work wonders, as well. Only one or the other of these nerfs though, not both; either make it take as much effort to set up rocks as it takes to get rid of them (there's a reason few people complained about Spikes and the rarity of rapid spin in gen 2 and 3), or make it as trivial to remove as it is to set up.