That's a good find. 0x0A as Arthur makes sense.@FluffyQuack I think 0x0A is for Arthur in SC1 but I only found that through google and not through any digging of my own.
"000A = Cassandra? (lifebar reads Arthur)" from the above link. The link theorizes that the cut character Edgardo is for 0x21
Also I wonder what Devil Jin's ID number would be...
I'm too lazy to double-check this by looking at game's memory, but based on one list I think the boss variants of characters in Legendary Souls and Devil Jin are immediately after Kilik. So it could be something like this:
0x3D = Kilik (SC5)
0x3E = Siegfried (boss)
0x3F = Cervantes (boss)
0x40 = Nightmare (boss)
0x41 = Devil Jin
0x42 = Ezio
That means some of these replace slots used for the bonus characters in SC4, but that's not surprising since they did replace bonus character slots from SC3.