SheepShaver hasn't actively been developed since 2009, and the last recompile to target "modern" versions of OS X was in 2014. SheepShaver has no current developer, although a few people have poked at it over the years to add features they really wanted, usually things that could be tacked on without modifying the emulator itself. We may be getting close to the point where SheepShaver no longer works under a current OS, although it seems to still function under High Sierra.
I've long thought that passing Apple Events between guest and host would be a neat trick for any emulator, but it's unlikely to make it into SheepShaver unless you can convince someone with the skill and time that it's worth it.
The highest priorities on SheepShaver are:
Make it 64-bit functional
Fix the memory management
Fix the security model
Without those changes, its days are numbered. At least we've got QEMU-PPC under active development now. Unfortunately, it's unlikely to get Apple Event passing either, as that's something you need to bake right in to the emulator, and QEMU is multiplatform.