There's an idea I've been mulling over for a game that is BYOR-ish, tentatively calling it Bring Your Own Open. Someone's probably done something like this before, but hey.
The idea is that everyone brings a name for features of the game - roles, powers, items, alignments, elimination types, even phases or mechanics. These are then taken and turned into a very weird open game. Roles are assigned at random - you can't be sure you'll get what you bring.
The motivation is that there are a lot of closed and bastard games, and this forum has had some frustrations over initially hidden features of these games, especially in the context of BYORs. Something I particularly don't agree with is mod participations/feature creation after the game has begun. It's one thing if it needs drastic rebalancing or you've written the rules wrong, that's just a foul-up and I've been there - but designing it in feels like you're not playing mafia any more. I'd also say the subforum could do with more open or semi-open games.
BUUUUUUUUUUUUUUUUUUUUUUT people really like BYORS and chaotic mechanics and hats. Me included.
The details aren't fully there, but I'd like to see players able to bring things other than roles. Items are an obvious choice, especially hats, but I'd also like to see players bringing alignments, powers, elimination types, "mechanics", and so on. Players wouldn't be able to specify what the feature they brought would be, but a sincere effort would be made to include whatever was brought in the game.
Of course, you don't want to end up with a different elimination type every day and seven different factions, even if it's an open game, so a cost should be imposed for each feature you bring to the game. Players could have ten coins, say, and could spend them as they liked on features of varying cost. Bringing items would be cheap, while roles would be expensive/limited and elimination types, mechanics and alignments would be very costly. The money would all be spent pre-game, and would have no connection to the actual gameplay.
Not sure what else would be available to purchase - roles should be assigned at random and it's an open game, so nothing that can be used in the actual game.
One idea is boosts - modifiers for the things you bring. Maybe a simple boost to make it more powerful/important to the game, a Death boost to give it more killing power, an Ultra boost to make it uncircumventable, a Meta boost to make it influence other mechanics, a Meme boost that forces the GM to reference insufferable mafia subforum memes in the flavour, and so on. Boosts would also cost money, so maybe you'd give up bringing a role and an item, and just bring a boosted role instead.
Obviously this would be a nightmare to balance and run, but it might be an open game that nonetheless satisfies that BYOR craving.