I don't know about putting one on a lease car, but how are they no longer fashionable, or rather, sought after? Have you tried to buy a nice low digit one recently? I'm just glad I bought all of ours a long time ago.
If you are set on getting one, I think they should be as short as possible. The current style AC19 ABC, may be personal to the persons whose initials they are, but to everyone else they just look like every other stock plate.