For me, the M5 is already at the upper end of performance for a super sedan -- with more power, I think I would only get in trouble. Most of my dream list revolves around luxury and tech updates.
dynamic rear axle steering and inner rear wheel braking
Variable distribution all wheel drive
Dynamic, self-inflating side bolsters
a valet mode, where the car wont go above around 3500 RPM and 30 mph.
Fully customizable, non-baffled exhaust -- options to open or close valves, to have "piped noise" on or not. On that -- if you can add noise, why not put in a form of active noise cancelling for when you want it absolutely quiet? It would be nice for taking a phone call or having a conversation.
Full IPS instrument panel - New vette, Porsche, LFA, other are really jumping on some amazing display tech that BMW could easily integrate right now with the correct screen.
carbon fiber trim as a option -- every other M now has it, why not the 5?
contrast stitching options like in the M6 and the new M3/4 without the exorbitant individual cost.
a no sunroof CF option
a spare tire OEM that fits - sell it as an accessory, I don't care... there's just some times I want that thing in the trunk when I am driving in the middle of nowhere.
digital display of oil temp
front radar vs camera sensing of vehicles
realtime map and speed limits updates over cell network ala Waze.
full iOS integration to actually show mirror iphone display on center panel.
Much bigger HD for lossless files
front camera to be included in the surround view ala the new X5
car already has front camera/gps/HD and an emergency sensing system... why not have a realtime recording system in case of crash/robbery/etc? If the car kept a 2 minute buffer of the 4 surround cameras along with position/performance/speed/time specs it could be a valuable resource.
As for the paddles, I am sure that if there was enough demand these guys could make them... IND and EAS both sell their products:
http://www.bmwpedals.com/paddles.html
Anyways, Monday morning dreaming over...