I've created a board game with definite rules and a winning condition. It doesn't (yet) exist anywhere other than my notes.
If I provide the complete rules as part of a question, and then pose the puzzle,
This kind of creativity is very welcome here on Puzzling and sounds like it would make for an interesting puzzle question.
While the brief for MTC 7 does admittedly specify 'Create a puzzle about a real world board game' (emphasis mine), I don't think there would be any serious objections to a question about a new board game with a well thought-out rule-set. After all, what does 'real world' truly mean here? I would argue that although your conceptual board game may not be available in the shops, the fact that you've been able to conceptualise it - thus making it hypothetically 'real world' in a 'perfectly playable' sense - would make it a perfectly legitimate contribution to this challenge.
The general attitude towards the MTC briefs in this community tends to fall more on the relaxed 'side of the fence' - it would be a shame to have an interesting question about a board game (shop-buyable or otherwise) this month and for it not to be a part of the challenge collection... Go for it!
