I have one too. I can confirm what you said about not working with digital
devices. One note for MS Sidewinder 3D Pros, it will work with that one
because it has a built in analog mode (but it kept activating itself and
disabling my wheel causing an instant left turn into the wall). I now have
a Precision Pro and it didn't work at all with the switchbox (just an
experiment, I use it through the USB port now).
You may find a "hardware" type db15 switchbox at your local electronics
I built last year and right now it is on my wife/son's computer and my CH is
sitting in a drawer so I could sell you the hardware one for what it cost me
to make it plus shipping. One note, it is only capable of switching between
two devices, but you should be able to chain them. The only part of it that
is home made is the wire from the switchbox to the midi port, which if you
don't like my job or it doesn't hold up, you can order that wire pre-fab for
about $7 or $8, it was just out of stock when I made mind (had to make it
work that day and all (attention span of a puppy)).
Hope I have or can help,
Rick Miller (Arrowhead)