Timing it like this avoids the issue of them being able to tap their lands and float colored mana in response, since theyll lose it when they move from upkeep to main phase
Let's make it a reality
Thats the bread and butter of reprint logic, right there
Use Full Heal, Scoop Up, or Switch
15.3 In bidding for any Lot, prospective Buyers agree that they have not been induced to make any bid by any representation, to the extent the representation is not misleading or deceptive, in respect of the Lot by the Company, including any representation arising from a document that has been provided by the Seller to the Company in association with the Sale of a Lot and made available by the Company for inspection by prospective Buyers
If youre lucky, you can cast a cheap spell of your own, counter it, and resolve a huge Eldrazi or other busted payoff super early in the game