While this is mostly a recreation of my Bowser sound hack for Smash Wii U, some voice clips from that mod have been replaced for the Ultimate revision; examples include his down smash and one of his victory animations.
The mod has been tested, but at this point in time, it's not entirely complete; I have to also figure out how to modify Bowser's sound script data, which is something that I lack the necessary knowledge to do. If anyone can help me out in regards to sound script data modifying, I would greatly appreciate it.
Sound Script Update
I've finally been able to modify Bowser's sound script data, and as a result, he's now more vocal when attacking. A few new voice clips have been added onto the .nus3audio file as well.
Skyline is required to use the script edits, so be sure to read the readme.txt file that's included in the download for installation instructions.
Sound Script Update 2
I've made additional sound script modifications for Bowser. They mostly involve the use of battering items, such as Lip's Stick and the Star Rod. Of course, for some actions, I did have to alter the voice clip timing.
Sound Script Update 3
Thanks to some useful information by Discord user Ayerbe, I was able to update my sound script edits further. Now, whenever Bowser performs a tilt attack, an aerial attack, or a throw (excluding the d-throw), the attack voice clip that plays will be chosen at random; either attack01, attack02, attack03, or attack04 will play, but there's also a 1/5 chance of not hearing a voice clip play. Similarly, there's now a 1/2 chance of hearing the jump voice clip when performing ground jumps, and a 1/3 chance of hearing the ottotto voice clip when standing near a ledge.
My sound script edit to Bowser's second victory animation did get removed during the process, since it's rather difficult to hear the voice clips while Bowser's victory BGM is playing.
On a final note, no changes have been made to the .nus3audio file.