It's slightly different rules for multiclassing. If my Monk (Way of Shadows) 6 takes a level of Fighter, they're not a Monk (Way of Shadows) (Fighter) 7, They're a Monk (Way of Shadows) 6/Fighter 1.
I fully intend on reading the VMC Warlock you have up after the contest runs, but it's not a subclass, so, again, I'd disqualify it if I were in charge. I'm not, so my opinion isn't really valid, there. Again: I would not have brought this up had you not specifically asked for people's thoughts. Take or ignore my thoughts as you will. They've been given, as requested.
Okay. I went back and made sure to read it throughly, just to give you a fair shake, because, who knows? I might have been way off and not giving you a chance just based on the name! That would be silly of me.
I still don't like it. It's far too much book-keeping and essentially ports over Fourth Edition's rules on multiclassing, allowing you to multiclass instead of subclass and...
I get it. I get why you might want to do this. I just don't feel like it fits with the point of subclassing. It feels like this for for when you want to have your multiclassing cake and eat your delicious level 20 capstone ability cake, too.