Of course completely awesome to make a modification like this.
However, if you yourself want a USB SNES controller, consider buying one instead. 8BitDo offers them with the SN 30 Pro - the quality is good, they work with the Nintendo Switch or PC (including Linux), they have the additional buttons needed for modern games, there is a wired and a wireless version and the newer variant has afaik a replaceable battery (unlike the first).
Edit: I was probably wrong about the replaceable battery, that was the 8BitDo Pro 2. Which might indeed be the better choice. Looks less like a SNES controller, but at least still has the correct button labels and core layout, see https://www.8bitdo.com/pro2/
I did try different 8BitDo controllers, and one issue with them is the "multi-mode": in order to make them work with Android/iOS/Windows/whatever, you need to press some key before connecting them, to change the way the OS recognizes the input. Which is a deal-breaker for small children, and prevents keeping things simple (e.g. "remember to disconnect and reconnect the USB before turning the power on", e.g. when using a Raspberry Pi-based console emulator). For wireless controllers, it's even worse (extra Bluetooth mode). If only they had mechanical switches to select this behavior... You may need to keep the instructions booklet with it, just to remember which keys must be pressed before turning it on, to see which mode will be activated. The controller in TFA is more useful in this scenario, since it will always behave in the same way.
The ones I have (SF30/SN30) remember which mode they're in so I just press the start button and it connects to my Switch. Then if I change it to bluetooth, it's the same for my Steam link until I switch it back. Plus there's a sticker on the back that gives the combos to change modes (Y+Start=Switch, X+Start=Bluetooth, etc). Some models, like the Lite 2, do have that physical mode switch.
I have four of the bluetooth SN30's for couch co-op games on my SteamDeck. I agree that if I switched between devices often (like my son's switch) I'd need a lookup table for the power-on chording. Mine have the key combinations printed onto the label on the back.
Fwiw, the ones I have remember their last pairing setup, so I only need to power them back on via the "Start" button.
Completely agree. I even had that situation myself - I misremembered how the mode switch/bluetooth pairing mode worked and was not able to connect my controller to a switch, thinking it was broken, until I realized what had happened. A small toggle switch really would be much easier.
Still think it's worth it, also to not destroy an original one. On the other hand, better to modify it like this than to throw it away of course...
The new version does actually use a switch instead of the magic button combination. Agreed on the previous version being annoying. Had many kid debugging sessions when they accidentally switched the mode and “broke” it.
I speed run Zelda 2, though using an SNES controller. My experience with 8BitDo controllers is that they're stiffer than OEM, especially with the d-pad arrow keys. If you can use the analog inputs, they're great -- I use a Pro 2 with my Switch all the time. The d-pad, though, is a deal-breaker for classic gaming. iBuffalo used to make a controller that really did feel like OEM, but they've been out of the business for a few years.
Can only recommend the iBuffalo SNES controller too, I have two of them and they are quite good. Didn't know the brand stopped making them, it's a pity.
Maybe if you want to play super mario, the 8bitdo sn30pro works.
But it has a huge problem of false diagonals, making is absolutely worthless to play tetris, or any fighting game that requires precise control. If you need precise controls, avoid this model.
I have the SF30 Pro since a few years now and there might have been different revisions, but I definitely did not observe that. And I played through Hollow Knight with it, so I doubt that the controls are imprecise - I would not have had succeeded. Granted though, neither tried Tetris nor a classical fighting game.
8BitDo makes great controllers. I have an SN30 Pro, a Zero 2 and a pair of Ultimate Cs. All of them have been used extensively and they are all excellent quality.
On the other hand I've had back luck with generic NES and SNES knockoff USB controllers. The quality is much worse than the originals especially in the D-Pad. It seems nobody but 8BitDo can get this right.
If you stick with 8BitDo you'll have great quality but they don't necessarily match the form factor of the originals. I can see why OP would want to convert a real one.
The form factor is really close though. Ignoring the added buttons, which is completely possible while gaming, it does not feel much different. https://www.onli-blogging.de/uploads/sf30pro.jpg for an example picture :)
I'm using the 8BitDo wireless pads on my Switch and am very happy with them— vastly more comfortable than joycons, but a fraction of the price of the official pro controller.
However, if you yourself want a USB SNES controller, consider buying one instead. 8BitDo offers them with the SN 30 Pro - the quality is good, they work with the Nintendo Switch or PC (including Linux), they have the additional buttons needed for modern games, there is a wired and a wireless version and the newer variant has afaik a replaceable battery (unlike the first).
Edit: I was probably wrong about the replaceable battery, that was the 8BitDo Pro 2. Which might indeed be the better choice. Looks less like a SNES controller, but at least still has the correct button labels and core layout, see https://www.8bitdo.com/pro2/