Other cards to consider cutting are Wild Growth (there are better ways to ramp with slivers), Prodigious Growth (which is not needed on slivers, as they all pump themselves), and Awakening Zone (which is too slow for how fast sliver decks want to move and not needed since most slivers have a low mana cost)
If you want to upgrade on a smaller budget then just make less swaps: Additions: Cuts: The deck comes out the gate faster thanks to a streamlined ramp package
Commander players the world over enjoy artifacts that cost 0, 1, and so on at every mana cost
Rooms are a mechanic in a subset I call "two-in-one cards." These are cards that represent two cards but exist on a single card, although possibly on both faces
Maybe a strategy of 'securing spells from here' is viable
Introduces the first support for the "Gate Guardian" and "Labyrinth Wall" archetypes