Personally for me, this makes for somewhat uninteresting gameplay to watch, and the subgame of who gets to resolve W6 first is quite frankly a little boring
If our opponent counters, Thoughtseizes, or destroys combo pieces like Altar of Dementia or Thran Vigil, we can always use Lurrus of the Dream-Den to play them from our graveyard
Tutors In a 99-card singleton format, tutors are a powerful way to add consistency to your decks
Creatures (26) 4 Lotleth Troll 4 Chromanticore 4 Soulflayer 4 Zetalpa, Primal Dawn 2 Murderous Rider 4 Questing Beast 4 Gingerbrute Lands (19) Spells (15) There are a number of different ways to build around Soulflayer, but most of them are going to be playing the big payoffs
Further Upgrades The first cards I'd pick up to further juice up the deck would be untapped mana-fixing lands: Watery Grave, Shipwreck Marsh, Underground River, Morphic Pool, Darkslick Shores, Polluted Delta, Sunken Ruins, Undercity Sewers, Urborg, Tomb of Yawgmoth and then maybe a couple more Island / Swamp fetches