Look at Nightmare, that went well.
Fun fact: none of Nightmare's "co-creators" listed are actually co-creators as far as I know.
The only reason I got was listed was because I was willing to put in an hour to make one of his earlier quests look less like tile error'd half-ass garbage, and then he started listing me as co-creator on stuff I'd only beta-test (New Quest Rebuilt? I only beta-tested it. That's all). And don't get me started on Gleeok: I highly highly doubt he helped James beyond beta-testing and advising.
All of Nightmare's quests are either re-submissions of his first quest with some changes, re-submissions of a dev member's first quest with some changes, or re-submissions of 1st.qst with some changes. tl;dr Nobody truly collabed with him.
What are you willing to do in this collab? If your only answers are "story" or "ideas" or "layout" or etc, then maybe you should take a giant step back and contemplate why nobody has made you a quest yet and why nobody who did accept has gotten back to you yet. No, actually, take a giant superstep back and contemplate on what the hell a collab is. You're reminding me of 2014 Dimentio, who wanted someone to make him 2 24x24 overworlds 2 16x16 overworlds and 2 8x8 overworlds in DoR; and frankly you aren't going to get on anyone's good sides by acting like 2014 Dimentio.