As I said, I don't care about stereo because I only listen to music on headphones, and those would retain stereo functionality. Essentially all I want from the speaker(s) is to ring loud enough for me to hear the phone, and I need to know if a one-speakered N900 will do that loudly enough.

There is reason for the USB thing. One doesn't typically walk around with adapter cables in one's pockets; having a full-size socket would make it possible to, I dunno, plug someone's USB thumbdrive and share some music without having planned to do so, or grab some data from them to later be transferred to a computer.

As for vandalism... well, I have a long history of performing similar hacks and I've never minded brutalizing my gadgets to improve them, functionally if not aesthetically
Only reason why I don't stick an external port on some kind on the N900 is because I want to bring it on planes, and airport security tends to be unhappy about things with wires and melt-glue sticking out of them...