This would likely require a couple years of widely printed Modern and Legacy Masters sets, and yes, the reserved list would have to go
Giant Adephage makes 7/7s with trample, Omnath, Locus of Rage makes 5/5s that will deal extra damage when they die, and Crested Sunmare makes 5/5s just for gaining life
Reckoner Bankbuster makes creatures to help crew your stuff and Mechtitan Core lets you build a freakin Megazord
He can show up, steal a big creature , and use it to win the game, or he can just be the last part of a mana combo that causes everyone else to lose infinite life
When it comes to instants, Akromas Will is important in protecting our creatures from board wipes, though it can also be used as a game-ender by granting double strike to our creatures, making it a very flexible and multifunctional card
Gandalf the White Gandalf the White is a nice addition to both Teysa Karlov and Elesh Norn, Mother of Machines decks, but I think theres a decent build of this Mithrandir as a commander of the kind of deck where you run Teshar, Ancestor's Apostle