
If you don't want to have a USB hub dangling off your USB host shield you could get a keyboard with a built-in hub and plug the mouse into that. Or you can still get PS/2 keyboards and mice, so you could have a go at implementing a PS/2 interface - I don't know if that's feasible using interrupts directly on the MicroPython board or if you'd need another chip to convert it to a friendlier format. A PICAXE-08M2 can easily be programmed to read keypresses from a PS/2 keyboard and output them via serial, I2C etc.