One word - Ara. Then I could do with my phone what I do with my desktop - replace parts so it's usable for 10 years.
What I'd really like to see is some new battery technology - the electrical specs of a lead-acid battery with the weight of a lithium battery. Drain it to 0%, and if you charge it within a day or so you didn't hurt it. Maybe more power density too, so I could go a week on a charge.
Removable battery and SD card slot (if for nothing more than resurrecting a hard-bricked phone), of course.
@B. Diddy:
It takes about a minute to debloat a Note 3 - copy the debload script files to the phone, run the script and come back later. (Not that I need to yet - I still have over 22GB free, and I'm a software junky. I just froze a lot of the bloatware, so I don't have to wade through it in the app drawer.)