Your argument majorly fails where it doesn't address the fact of all other pieces in the 'combo' here are potentially open to removal.
But they're not, though.
Using only cards within my physical reach, this combos with Aerie Ouphes to repeatedly kill all flyers on the board forever, even with spot removal. (EDIT: I nearly forgot, it makes infinite mana at the same time.)
I'm sure it's equally broken with any number of Undying / Persist creatures and/or sac outlets.
You can actually cast Diregraf Rebirth for only BG twice if only 5 or more creatures died on the turn you cast it. It doesn't reset the count for each cast.
It doesn't say much for a purported removal spell if its best use is putting it on my own artifacts and enchantments to give them shroud.
Put it on my own Platinum Angel, now it can't be forced into combat.
The templating of this ability needs work. It really should be "You may reveal ~ as you draw it. if you do, you may pay (cost) and exile ~. If you do, (effect)" but that's so clunky.
Maybe more narrow but more elegantly:
Telepathy (cost) ((Cost), exile ~ from your hand: You may activate an ability of ~ without paying its cost.)
I think it's important for this card to not be different than the other Hideawsy cards, but at the same time the Commander deck this wants to be the Commander of would definitely run Strionic Resonator and the like. I prefer the "cast a card" wording for now, just to prevent brokenness.
I like the idea of the cost scaling to the spell's mana value.
Revision 2:
Hideaway Elemental 2GRW
Legendary Creature - Elemental Avatar
Each land you control enters the battlefield with a cove counter. As long as that land has a cove counter, it has hideaway and "X,T: You may play a card exiled with this permanent without paying its mana cost if its mana value is X or less."
3/3
That's the cleanest way I can think of to make it so you don't need the creature to be able to cast the hidden spells. Does this ability work correctly? Specifically, with this guy out my lands will have hideaway in time to enter tapped, correct?
Lands you control enter the battlefield tapped.
Lands you control have hideaway and "3, T: You may play the card exiled with this permanent without paying its mana cost."
3/3
Wanted a commander that gave all your lands hideaway. I wanted to let you play the hidden cards even if the commander wasn't on the battlefield but I can't think of an elegant way to do it without counters. Cost or conditions to play the hidden cards are up for debate. "Lands ETB tapped" is technically redundant to Hideaway, and could be dropped if the reminder text for hideaway was included.
If your life total changes then by the rules you gain or lose however much life. Yes, you need to spell it out like that. Other cards care about players losing or gaining life.
What do you mean, during that turn your life total becomes 1? You mean they lose all but 1 life at the beginning of their upkeep, and gain that much life at the beginning of the end step?
But they're not, though.
Using only cards within my physical reach, this combos with Aerie Ouphes to repeatedly kill all flyers on the board forever, even with spot removal. (EDIT: I nearly forgot, it makes infinite mana at the same time.)
I'm sure it's equally broken with any number of Undying / Persist creatures and/or sac outlets.
Put it on my own Platinum Angel, now it can't be forced into combat.
Maybe more narrow but more elegantly:
Telepathy (cost) ((Cost), exile ~ from your hand: You may activate an ability of ~ without paying its cost.)
Legendary Land
You may play one additional land each turn.
(No mana ability.)
Revision 2:
Hideaway Elemental 2GRW
Legendary Creature - Elemental Avatar
Each land you control enters the battlefield with a cove counter. As long as that land has a cove counter, it has hideaway and "X,T: You may play a card exiled with this permanent without paying its mana cost if its mana value is X or less."
3/3
That's the cleanest way I can think of to make it so you don't need the creature to be able to cast the hidden spells. Does this ability work correctly? Specifically, with this guy out my lands will have hideaway in time to enter tapped, correct?
What about the colors? Should this be Jund?
I know, I said so in the OP that it was redundant. I figure it's part of hideaway everyone forgets about so I spelled it out.
Legendary Creature - Elemental Avatar
Lands you control enter the battlefield tapped.
Lands you control have hideaway and "3, T: You may play the card exiled with this permanent without paying its mana cost."
3/3
Wanted a commander that gave all your lands hideaway. I wanted to let you play the hidden cards even if the commander wasn't on the battlefield but I can't think of an elegant way to do it without counters. Cost or conditions to play the hidden cards are up for debate. "Lands ETB tapped" is technically redundant to Hideaway, and could be dropped if the reminder text for hideaway was included.