Not that i would add these in my cube, but i would rather see these in my deck / sideboard: Basilica Guards, Jeskai Barricade, Wall of Resurgence, Puncturing Light EDIT: Wall of Resurgence might actually be sweet enough that i could see it in my cube also
They provide not only a tangible reward to the player running primarily Mountains but punish the numerous multi-color value piles that seem more and more prominent
BPhillipYork: This isn't really a new mechanic per se, we've seen it before with germs and other equipment that creates a creature
The Walls of Ba Sing Se Speaking of high mana cost, colorless permanents that work well in a wide range of different decks, meet The Walls of Ba Sing Se, and yes they are tall, aren't they
Beyond the collection support, Spellweave also does a lot more actual deck optimization than most Commander tools