Here are some of my ideas:
Detachable keyboard. It is physically possible to make the keyboard into a little 'pattie in a sandwich' that sits exactly where the current keyboard does but can be removed to make the phone thinner for people who dont use it a lot or to sell a thinner version of the phone at a lower price. Also, the keyboard would be easily replaceable if damaged and I guess people could buy foreign keyboards then if desired. Basically the only thing this would require is a different method for attaching the screen to the main unit. then the keyboard piece could snap inbetween to the main unit like a docked laptop.
Peripheral support for mini usb port. It would be cool if we could buy an adapter to make the miniusb port into a full usb port and there were standard drivers included for usb keyboard, mouse, thumb drive, card reader, and the ability to make and market third party devices. Card reader might be most useful.
Wireless G router mode. Ability to share EVDO data connection over wifi.
Louder speaker. Come on. Spend an extra 50 cents on the speaker. It ought to be loud enough to hear even in a car on a bad highway at high speeds.
Also, it is worth noting, DO NOT GET RID OF STYLUS. STYLUS IS NOT DORKY. If you make the interface more finger friendly, great, but the stylus isnt taking up too much space. If you want to get rid of something, I have never used IRDA. It may as well have a parallel port as IRDA. Get rid of that. Also, an extra microsd or miniusb slot could never hurt.
I would also like GPS and more memory. Some of these other ideas are more unlikely.
I also had an idea about GPS. Maybe you could make a GPS device that fits in with a regular battery in the size of an extended battery and gets juice from the battery. It could somehow tap into a small data port, or for the
Mogul have bluetooth. Then it would be sort of internal. For a new phone you could also offer GPS as a premium option like this, or you could integrate it into a premium version of the detachable keyboard I mentioned.