This would be better suited to the RAthena Development board since we're going into the idea of new functionality, rather than a true software bug (the issue itself is a client exploit technically).
It happened a few complaints on my server on an issue. GRF, to edit. ACT skills of the players managed to remove the delay of the skills that had the file. ACT edited. I tested using the time. GRFEditado and time without using it. GRFEditado. Actually the delay is reduced even the low amount of SP faster.
PS: if you want to. GRFEditada only comment I send the link.
I imagine it'd take little effort to write an ACT parser to read the animation length for the damaged and skill-cast frames, and convert that into a separate database or as a new column in the skill_cast_db.txt, I'll see what I can muster up.