The series is just disjointed as no one could agree with what anyone else wanted to do.
I thought he looked like Aizen. There was a fanfic that tried to showed what would happen if he didnt have moka's protection. Its pretty great.
its not that great.
D Gray man could work if you iggnore the time differences.
In a crossover, I'm perfectly happy if the core of the character remains the same. The details of the background are... mutable. For example, I'm not going to complain all too much if Dante and Vergil were recast as something more mundane than actual demons (genetic engineering style, some special brand of artificial human or whatever), as long as they both still acted like Dante and Vergil. And there was stylish action involved.