I'm not sure if I completely understood your original post but I kinda took from it that you're looking to keep your existing 8 way fight stick and then buy another cheaper fight stick to modify for 4-way?
If that's the case, why not just buy a cheap fight stick and change out the joystick itself to a Sanwa JLF with the restrictor turned for 4-way (diamond pattern).
I know most people mod their fight sticks with the smaller Asian type mounting plates such as the JLF and the Seimitsu and Zippyys.
If you're looking at having a best of both worlds fight stick with both 4 and 8 way switch ability than maybe as said above you can use a Zippyy and just set the restrictor for what's needed at the time.
If the fight stick has a removable bottom, maybe you can leave it off for easy access to the restrictor.
I remember reading something around here once where someone used rare earth magnets on their restrictor plate rather than the screws. If you did something like that, you can play fighters and what not with the restrictor removed and then slap it on when needed for 4-way
I'm not locked into either solution. I'm educating myself on the options right now, just learning what I have available to me. I have this stick, and I like it fine for the gaming that I do in 8-way, but it's not great for 4-way games. I'm open to modding the stick to make it dual function, or picking up another cheap stick that either runs in 4-way (or dual) or could be modded to a 4-way. As I've looked at modding the fight sticks I can get for cheaper, I'm running into the differences in the plates for these different stocks and the challenges of drilling holes in plastics for incompetents like me. Looking at something like the X-arcade, which seems to have a nicer build, this discussion has let me know that their product doesn't quite do what I want (since the 4-way play is not restricted), and so it would need additional modding.
For the stick I have, if it could be modded to add a stick that would work well in both 8 and 4, I'm open to that. Your magnet idea intrigues, as the options for switching from the top are pretty limited.
I'm not sure yet where I'll wind up on this. You guys are very helpful in educating me on the options, though, and I appreciate it greatly.