I also do not currently own a 5th gen but have rented both a 1LT and a 2SS for a week each. So based off the limited wheel time my recommendations would be:
1) Better interior lighting
2) Fully adjustable passenger seat and seat memory for those of us that would occasionally be required to share (you know that spouse thingy)
3) Improve the DIC to be a bit more user-friendly (meaning you don't need to read a huge manual to figure at least the basics). Nav w/screen
4) Definitely climate control. During my rental periods I did notice I was constantly having to fidget with the temp to be comfortable.
5) Driver/Passenger Seat Belts. This is probably my biggest request. I would like to see the seat belts configured like the ones in the convertible concept for both the coupe and convertible models. Having the shoulder strap move forward with the seat greatly increase accessibility to the rear seats for both passengers and cargo. Several other manufacturers have similarly seat mounted belts.
Regardless of all the items on my wishlist, I've never been so excited about a vehicle. Waiting for the convertible (and final production details) has been excruciating.