Why not both USB *and* more serial ports? You did say "ideal".

I'd like to see some of Noritake's multicolor VFD technology incorporated into the main display. Heck, I wouldn't mind seeing a double DIN empeg with a larger screen.

Of course, that brings up theft prevention -
the new empeg should have a metallic faceplate that is switched between Ground (normal operation) and a nice fat inductor coil that charges to... let's say 40KV as an example, when it's internal alarm is armed. When the alarm is triggered, it turns the empeg on and plays "Help! I'm being stolen" repetitively at ear-drum splitting levels, or alternatively plays 'I should be so lucky' by Kylie Minogue, at said levels, which should be enough to drive the would-be thief insane. The alarm is key-locked with a crypto iButton.

Oh, an integrated GPS, OBD, radar detector, and a CF or SDcard slot for live data logging would also be nice.