While i agree that it must not interfere with the development of GT6 in any way (just do GT6 first and then do a straight limited port), i would very much love to see GT on Vita.
GT psp is a blast, i honestly don't get why people lambast it for having no career mode, the game setup is so streamlined; pick a car, a track, set laps, off you go. That honestly all you need in a portable game and wish GT5 had something this userfriendly!
The only big concerns I have are how to solve the fact that there are no analog triggers on the Vita for modulating throttle/brake input, and having no rumble.