The price of the deck can be lower. It can also be setup to be played against a single opponent, and be twice as frustrating.
Deprive- Awesome hard-Counter for running any of the mill8 Crabs. Furthermore, this card replaces itself with a land before triggering Jace's Archivist. More for 1v1 purposes.
Folio of Fancies- A 2-drop enchantment that can be used later in the game to target all opponents with a Jace's Archivist-type effect. Also, while the draw synergizes well with Archivist to build up hand numbers, it's rarely used as the double-X cost is a bit high, but does proc any Draw=Mill enchantments. I suggest only 2 of these should be added in place of or Jace's Erasure for multiplayer games.
Fraying Sanity- 1v1 win-more card. Mills double the cards put into the opponent's GY at the end of each turn. Used in place of the multi-opponent hitting Psychic Corrosion. Only 2-3 of these are really needed in the deck with the draw engine.
Hedron Crab- For 1v1, and budget replacement for Ruin Crab. Hitting only a single opponent for the same 3 cards with a little less stopping power. This was my little buddy for a long time in many mill decks, until his bigger brother came along.
Jace's Erasure- best for 1v1. This was mainboarded originally, and has exactly the flavor I want for this deck; but was replaced with a multiplayer-alternative. The cheapest draw=mill enchantment. Only hits one opponent per draw, but can do some heavy lifting over the course of a game if it's out early enough.
Jace's Phantasm- once the game gets past turn 3, you may be in trouble if facing an aggro boardstate. This becomes a 5/5 flyer as long as your deck has been doing something it's supposed to be doing. More of an alt-wincon, this flyer only costs one, and can put a turn clock on your opponents; or, at least distract them with presence, so they forget about slinging damage spells your face for a moment. Crab replacement seems best, purely for budget and availability in the meta.
Profane Memento- Great for multiplayer, or creature heavy 1v1. Also, a wonderful space-holder when lacking copies of cards that may be more expensive, or deck-solidifying, like Jace's Archivist, Ruin Crab, Serum Visions or Psychic Corrosion. Highly underrated card, IMO, as it makes up for the lack of speed with impressive longevity. I've often thought about replacing one of Teferi's Tutelage, Jace's Erasure, (and one Island) each for 2 (or 3) of these in the deck.
Remand- Kinda-hard counter for 2 + draw. Punishing your opponent for their attempt at a spell. This is good in place of Take Inventory. Not necessarily more budget, but synergizes well with Jace's Archivist.
Thing in the Ice
- As stated, creature heavy metas can be a problem for this deck. Why not put a big baddy out of your own? Starts as a 2 cost, 0/4 blocker for early game defense, and quickly flips to keep the board clean and an alt-wincon in your back pocket. This fits the curve nicely when you're building up your mill-engine. Replacement is suggested for Jace's Erasure, Ruin Crab or 3 cost enchantment. Works well just before using Jace's Archivist to build up draw numbers.
Thought Scour- A draw cantrip that mills a little. This can add some fuel to the deck if you lack or don't care for the higher cost draw spells. It can even make up for a little lost mill power if replacing an enchantment. It's a nice budget, cantrip or Psychic Corrosion replacement in 1v1 games.
More to come!