I don't suggest we include this for its own sake, but several of the suggested blue skeletons ran into difficulty balancing the number of and mana costs, not wanting too many, but wanting as many cards as possible to be reward mono-U decks.

If so, it occurs to me a couple of or mana costs may help the "reward players heavily for playing mono-U decks without completely screwing over people who splash". I suggest only using this if we feel we need it, but I think it might be useful if we do.

Good thought. As MaRo said, hybrid is a tool; one you don't want to use all the time, but one that's available for use sometimes if it's the right tool for the job. This could be such an occasion for monocolour hybrid.

That's not a bad idea. It's up at an awkward time, but I'm sure that we can work with it by just changing the casting cost of spells going into the skeleton. Shall I suggest that we do one per color in common, and always the same casting cost (for example , , etc..) to make it feel special? Any more than that, and I fear designers will feel that we should have been building around it, and want to go back and change too many submissions. It does give us plenty of space to monkey in the uncommon slots, though.

I don't think you need put it in yet at all, I think we should wait and see if UU and 2U mana costs work out, and only if we feel they don't come back and recost some using hybrid mana.

Sounds like a plan. It would be very easy to implement later, anyhow. I think I do like this better as "a tool that development can use if things are out of hand".