The KVMs use to emulate keyboard & mice - meaning you probably can't use it for switching Amiga peripherals. However, you can use PS/2 devices with adapters on the Amiga side if you really need to.
I'd build a simple mechanical switch for K&M (just data & clock for the keyboard plus 4 mouse lines and 2 buttons) - not extremely elegant but bulks of adapters aren't either.
