Multi-MIDI-IO?

I'm thinking of building a flexible MIDI merger / router / mapper using Arduino. I'd like to have 8 MIDI ports, which can be configured as input or output, and a simple routing / mapping table. This means eight serial connections at 31kbps each, with a very simple 8x16-entry lookup table to map input / channel to output / channel. This must be done in real time; delays upwards of 15msec can be "felt"/heard when playing.

The rest of the inputs would be used for buttons/footswitches to switch between mappings, maybe output arpeggiator clock, maybe interface with an LCD.

I've seen examples using the serial port code on the net. They look great, but from what I've seen, they only use I/O pin 0. My questions are: a) Do you think Arduino can handle this task within the timing constraints? and b) is there a library that lets me do serial interfacing with the other pins as well?

Any help is very much appreciated.