Well, I've not looked at the board itself since you provide no (obvious) links to it, but...
RichCini wrote:
Maybe changing the miniUSB power jack....
Changing your Mini-B receptacle to a Micro-B receptacle would probably be a good idea. Not only has the Mini-B been deprecated since 2007 (Micro-B cables are significantly easier to find), but Micro-B has twice the minimum number of insertion/removal cycles (increased from 5,000 to 10,000).
Quote:
...to a USB-serial adapter which then connects to the ACIA. That eliminates a MAX232 and caps. Need to watch the power consumption, though.
I think that's a pretty good idea; I don't use RS-232 levels on any serial interfaces any more except old computers that don't do TTL serial.
As Martin_H points out it's also a good idea to keep your serial header on the board, allowing the board to be powered from USB but do serial through a separate link. You would probably want a jumper to disable the USB/serial chip in case someone is powering it from a host device using a cable with data lines but wants to use the header for serial.
If your serial header doesn't already include +5 V, adding that would allow you to have a separate MAX232 board to plug in to the header for applications that need RS-232.