sedirex asked:

Stopping 5-color soup seems pretty simple tbh. Just give a bunch of cards upsides that you only get if you control no (e.g.) green permanents or lands that produce G. And cost them so they're not worth playing without the upside. Is there some other mechanical issue?

That solution has numerous issues. First, it’s not as easy a thing to define as you think. Second, it would be wordy and doesn’t leave you a lot of room to do other things. Third, it cuts you off from using five-color mana fixing which a four-color set would probably need (you most likely don’t have space for a cycle of four-color mana fixers). Fourth, it’s mentally hard to process if you have multiple different ones mixed together. Fifth, it’s not even that hard to play around - use artifact mana fixing for your fifth color and only play spells with it. Sixth, there’s only so many cards you can use this restriction on, so what do you do with all the other cards? And seventh, from a game design standpoint, it’s a bit inelegant.