The best plugins are caused by developers facing an issue, then finding a solution for this problem. They don’t do it for money, and they don’t do it for the sake of making a plugin either. They do it to solve the gap they’ve faced.
You can look around in #help-and-feedback and #feature-requests and see what developers are facing nowadays. Based on this, you may get ideas on how to turn an annoyance into a piece of cake.
“Would this get me banned?” => This is not a great question for the forum as forum users should not be expected to have authority to answer questions like this. It’s best to point these users towards the TOS.
“Touch Grass Simulator” => This sounds like a creations feedback thread to me.
“Give ideas for an arm wrestle style simulation game” => Sounds like Game Design Support.
“Team Green HACK/EXPLOIT” => Doesn’t really seem like it should be a help question, it seems more like a discussion thread at best.
“Look what ROBLOX did to our GRID SYSTEM!” => Seems ok in the discussion category, but otherwise could be in Platform Usage Support.
All in all it looks like the existing categories cover these topics well. Going to assume having the existing categories (incl. Platform Usage Support) is sufficient here.