Yes, the file needed is the one u showed earlier ( vincent's script, red13 etc) , the key to play as enemies is in this file, but there is a lot of things to change, thats very hard to explain in one post
Like Meesbaker said, u need to know the listing of every animations ( standing, hurt, dead, attack, magic etc), you know where the limit break are since you modified them already ( in the end of the file, starting with E0 most of times)
But there is other things to change, called the animations offset, all players share the same animations script offset ( with sometimes small differences, like vincent , he have only 4 limits break, cait sith have less , etc)
On PC the file structure is like this, its far more simple than on PSX :
1/model data information ( 68 bytes length if i remember well, not sure)no need to modify this part
2/animation script offset (u must copy paste a player animation script offset to make an enemy playable)
3/animation scripts ( since u erased the original offsets for a player script offet u need to modify the animations script as well, thats why u need to know the order of every animations) YOU need to know what value is what ( sry for my english :p ), like E8 = load effect, EE = end of animation, etc, i think NT1FC listed a lot of theses values somewhere in the forum.U need this to create your own animations script, because if u just copy paste already existing enemy' animation script that wontbe always exact,for shotgun like rufus, its more complicated u need even more values for the "fire" effect on his gun,the sound, etc.
Character like rufus can be played without problem, since they have the same size that playable characters, for huge bosses( like in my video) u need more steps.