The least of its problems
> one of the tiny ARM-based computer’s signal limitations: too few USB ports
In my experience, the number of USB ports on the Pi is a small matter. Ther are other design points that are more important to improve.
If anyone was planning on designing a "model C", I'd suggest dumping the Ethernet port, in favour of a Wifi device. Moving the ports around so they don't come out of all sides (possibly start by changing the SD card for a micro-SD), thus making it easier to integrate into other equipment. Adding some onboard flash, to obviate the need for an external card - though keeping the option for one.
It would also be nice if the board had (at least) a reset button, or, better, a header to break one out to a front panel. Do the same for some user addressable LEDs, so that the embedded version of "Hello World" doesn't need any hardware hacking and add an audio input port and you'd get to compete with the current best hobby SBC products like Cubieboard-2 and Olimex's A13