Ever since the release of "Attack of the Mud Creature 2" I shared an idea to messygirl for the next one. A Messygirl model feels alone since her friends "Amy, Misty, Vika, and Sabrina have become mud creatures. Every time when she sees and mud products she gets hot and horny. To clear her mind she takes a bath (or shower) and falls asleep and has an erotic dream where she is being initiated of becoming a mud creature by her friends. Before the mud covers her completely she wakes and sees a mud blob and gets really excited and says "If you can't beat it and just go with the muddy flow" and she starts smearing it on herself and gets turned on. When she's fully transformed she stumbles off to find the others.
I would pitch it to them and get a quote if you have the budget.
I've got several customs with several producers, including messygirl, but I only just commissioned them recently so they haven't come through yet.
I would suggest that you kinda storyboard your idea with pictures in a powerpoint so the producer can see what you want. Like your idea has the character thinking and feeling things and having motivations to do things, but its difficult for me to understand how that is meant to translate into something I can visually see, so I'm sure that producers might also get puzzled (or at worse interpret your idea differently than how you expected and execute without talking about it)
Or just make it easy and be like "Mud Creature 3 but with model X and Y" and let them go from there.