I'm pretty sure I've isolated the problem to purely because the Smart Card uses an MBC5 based memory chip where Pokemon needs an MBC3 chip (not sure but I think MBC1 is compatible too since that's what the japanese gen 1 carts have) There is an "anti piracy fix" like I mentioned in the thread migles linked that's supposed to give the games compatibility with Smart Card but only for playing on a GB/C whereas I think Pokemon Stadium is still trying to access the SRAM via an MBC3 chip.
I haven't tested other carts but apparently Everdrive GB works if you modify the voltage setting on your transferpak.
I'm pretty sure a GB Power cart should work if you manage to get a device to write ROMs to it (you can even add a crystal oscillator to it for GSC's RTC)
The last alternative is to get a cheap secondhand game that uses an MBC3 chip (I can't find a list of MBC3 games but last I checked Japanese Gold and Silver are pretty cheap and use it) and replace the ROM chip with a flash chip to make a homemade cart which like the GB Power will need a writer.
I did find a way to make Smart Card crash a lot less by simply putting the Smart Card on a Mega Memory Card attached to the Transfer Pak, sometimes it will ask to reinsert the cart when saving and sometimes it will get picky on whether I reinsert the Mega Memory or insert the Smart Card on it's own.
Also, for RGBY hackROMs, use the Stadium 2 GB Tower if the ROM's filesize is greater than 1MB (I haven't tested anything over 2MB which is the GSC filesize) as Pokemon Stadium 1's GB Tower only loads 1MB ROMs
Lastly the patch I mentioned above will prevent it loading in GB Tower at all so make sure to use a base ROM without the patch (some ROMsites out there provide it with the patch preapplied)
