Complexity of making a follow-up Estrus mod?

[v0rt3x21]

So I'm no modder and don't intend to start this up myself, but I'm just genuinely curious - the Estrus mod seems to remain very popular among those who are looking for a tentacle mod, but it also seems to be the only one (?) and is getting pretty old now.

 

What might be the major hurdle / reason why we haven't seen more tentacle mods or even an expansion to the Estrus mod with more animation?

I heard that animating tentacles is pretty difficult, would that be the only reason?

What about using animations from another source? or is that way more complicated than it sounds?