I'm thinking that Sylvester Shyster would've fit here better than Mortimer Mouse. I have heard Sylvester was a controversial character and was used in the comics more than animation before (nowadays he's exclusive only in European modern comics more often), but Mortimer is more of an anti-villain troublemaker than he is any dangerous. Sylvester was technically created by Walt Disney himself, is much more criminally evil and dangerous, has made plans on how to kill Mickey, and has occasionally partnered with Pete, and Sylvester is the one person Pete trusts more than anyone else in the Mickey Mouse universe.
Other than that, getting some serious "Terrible Trio" trope vibes from this fan art and I still dig it.