We need something frontend side to handle macro/autofire, currently the only way to do this is core side through core options, however it can be a source of netplay desync.
FBAlpha's core options to handle macro/autofire stopped working (https://github.com/libretro/fbalpha/issues/124), i don't intend to fix this, and will remove it completely instead, because it was never a good idea to handle it that way.
While i don't use it myself, i think this feature is important, and having this feature implemented frontend side would benefit all cores and solve netplay issues.