Is there a remote desktop software that works on the SE? Except for startup hotkeys, you could potentially type on a different computer to the SE through a network connection. It's not a good or permanent method but it might work in a pinch. Also, if you have KeyCaps (System 7+) you can type with the mouse and copy/paste as necessary, but this does not allow you to hold down any modifier keys.
Have you had a peek inside this adapter? Does it look easy to duplicate? I'm sure the firmware is protected... bleh... But maybe not, you never know.