I was having a hard time finding any solutions for this, so I decided to try on my own and discovered an easy way to inject SMS roms into VC using the Ultimate GEN-MD Forwarder, or the New Super Ultimate Injector 3DS.
Since it uses picodrive as it's main emulator core for Genesis/MegaDrive games, it also plays .SMS files, but the Forwarder won't read those. However, it WILL read .SMD files, and if you simply change the extension from .SMS to .SMD, it works perfectly.
So, if you've been looking for a way to do this all this time, like me, but couldn't find a solution, here it is. Try it yourself!
Since it uses picodrive as it's main emulator core for Genesis/MegaDrive games, it also plays .SMS files, but the Forwarder won't read those. However, it WILL read .SMD files, and if you simply change the extension from .SMS to .SMD, it works perfectly.
So, if you've been looking for a way to do this all this time, like me, but couldn't find a solution, here it is. Try it yourself!