I think whoever is best for the part should play it rather than the character matching the background of the actor. Trans people can put themselves forward for whatever acting parts they like and it should work both ways. I can see eg why Eddie Redmayne was picked to star in the Danish Girl rather than an unknown trans actor. He’s a fantastic actor and a big name. Picking someone just because they happen to share an identity-based characteristic with the character wont work if they can’t act.
In reality, in most cases, unless it is someone who passes as the opposite sex, their roles are likely to be limited to where the character is trans as otherwise the audience is unlikely to find it believable.