I agree with the switch to non-RFTs. I did this with my 2007 335i coupe and my current 135i.
I swapped the RFTs on my 335i for Hankook Ventus V12 Evos. I will admit that there was a small amount of squishyness (sp?). I increased the air pressure in the tires by 8-10 psi and the ride was fantastic. Great grip and handling.
My 2010 135i (CPO) actually came with Michelin PSSs and the ride is in no way squishy. Grip is awesome and the tires are relatively quiet. I am a big fan.
If money is no object, get the PSSs. If you are on a budget, try the Evo V12s.
You will never go back to RFTs.
BTW, I carry a Slime brand mobility kit in my car. It was about $70 at Autozone and came with a nice compressor, plugs, tools to plug the tire, and a bottle of slime if those options do not work.