The original sidewinder gamepads (gameport) had *plenty* of buttons, AND you could daisychain them AND they have nice labeled solder points/holes on their breadboard/pcb.
The way in which this is accomplished was to communicate with the PC in a way that is different than regular gameport pads communicate with the PC.
It works more akin to how MIDI signals work through the gameport.
It's my gut feeling that regular gameport gamepads (4 directions, 4 buttons) will work fine with your USB adapter. But I have my doubts about the MS sidewinder in that application due to the difference in how it communicates, and what the driver(s)/libraries expect from it.
*shrug*
Rampy