Poor Stanley. He needs his own ROM hack starring role to offset demands like this.
Okay, lemmee clarify this a bit.
Donkey Kong 3 is sorta not as popular as Donkey Kong and Donkey Kong Jr, I find that to be somewhat of a shame because even though it isn't all that unique in gameplay it is still a decent top down shooter type game with a lot of fun to offer. Putting Mario/Luigi in the main role adds some recognition because only extreme Nintendo nerds know who 'Stanley' is.
That's all, also, this isn't a demand of any sort, it's a suggestion in the hope that somebody who has the skills to do a pallate swap might find this an acceptable idea for a project.
Inserting Mario into games via hacking is pretty big tradition, Stanley is not the first to be replaced. Bomberman, Mappy, the star of lode runner, moai-kun and the balloon fighter have all been replaced with Mario/Luigi in the past. Those characters have not gone away because of these hacks, neither will Stanley.