I would like a new one with:
Faster main dual core CPU.
An I/O CPU/DSP.
A bank of parallel CPU's (lower end CPU's are fine), I want killer AI, in apps.
2D hardware mapped (for parallax displays, and scrolling, sprites - humour me I'm old skool).
3D hardware.
Lots more Ram (so all the app is loaded and running fast, if there are any files then set up a temp RAM disk - yes I am old skool, and I want slick apps).
Possibly some NAND memory.
SDHC slot.
A decent sound chip so there is no more crackling issues, and MIDI could be better supported too.
USB1/2 for external devices.
X & Y buttons + add another button (Z), to piss off the rest, (no more painting X & Y buttons on mine).
EDIT: Now I come to think of it move select next to start, and under ABZXY (Z- in the middle to form a "X"), put a phone type keypad for alphanumeric entry, just like on a phone - this will of course upset the dimensions a little (but all those extra function buttons in game).
Native support for things like chatboard etc, that devs have to code in.
A nice compact Linux kernal for the OS.
Correctly wired speakers.
Bigger back boobs (just kidding!).