16" 205/45R16 wheels will make the ride much more pleasant, because all tires in 17" sizes for our car (205/40 and 225/35) are Reinforced, XL (extra load), runflat, or another sort of devilish hard sidewalls that have absolutely no flex.
So just buy some 16" wheels and make sure you do not pay extra for Runflat tires, keep no more than 2.2 bar in them and you will glide along roads that now seem very harsh.
If you decide to turn your brab in a 100% comfortable cruiser, then downgrade to standard suspension, it's softer, and has more travel.
Whatever you do, don't sell. But if you do, trade it on here for a normal forfour, I'm sure you'll find somebody willing to trade up.