What would you like to see improved on the 5d Mk2?
For me it gotta be the autofocusing. Frames per sec speeds. SD card bay. Also, built in WiFi without the stupid cost or weight of the WFT-E4 mk2. Wireless flash triggering. Built in flash. Cornor loop for sling hook strap (freeing up the tri mount hole)
That'll do if for me