Regarding the issue about sound files... I played around a bit with the Cosmic Forge Editor, and saw that most sound files cannot be replaced per se. There is a SLF-file browser which lists all sounds in the game, but only for extraction - not import. There is a section in the tutorial on how to add new voices to a new NPC, but very tedious. Also this would only work for characters voices and not weapon sounds.
That said - even if it would work, it wouldn't solve the problem, because my assumption about the "2-second"-Bullwhip sound file was wrong. I extracted the Bullwhip sound file and it was just 0,5 seconds long. No idea where that huge delay in the attack comes from. Maybe something hardcoded for that weapon.
One thing that was possible to modify, was changing the "Weapon Matter" (material?) of the Bullwhip to "Dagger(Stabbed)", and "Attack Type" to "Thrust". Afterwards in the game the attack was slightly faster (albeit with the Dagger Attack sound - though it still remained a Mace&Flail weapon). Afterwards it was faster than the default Bullwhip attack, but not noticeably faster than Swords, Staffs or Kicks. So if you are not focusing on Bullwhips only, it actually doesn't matter much.
Another thing I noticed was, that I could change the sounds from enemies (Monster Editor), by clicking on the small Script icon for the Green Slime: there were approximately 4 different sounds available for each action (attack, secondary attack, special attack, dodge, die, move). I removed all SOUND_FRAME_entries and only left a single one for the attack (something like a "whip" sound, which was a very sharp and fast). But again it didn't change much or anything at all in combat speed.
The most annoying thing still remains, which is that there is a considerable pause when turns change between one enemy and the next. I guess this cannot be solved anymore.
