I dunno, I really don't have an opinion on what makes Slivers playable in Vintage. I guess I do know this:
1) To compete, aggro decks must have strong, meaningful interaction with their opponent. Too many cards that do nothing but beat face leaves you critically vulnerable to combo of various stripes.
2) If Slivers is to be a thing, it will have to be doing something very different from playing 12Lord.dec, because Merfolk already does that with more efficiency and a better mana base.
Beyond that, who knows? The Lantern / Screeching is really hilarious, and I love the concept of Turn 1: land, mox, lantern, screecher, go. To make that work, though, you'd better be able to deal with whatever they have in their hand or tutor up. It's no good to control the topdeck if a single Goyf or Tinker in their opening hand destroys you. That's why I think BU, for Duress and Force is probably the only way to go. If you go that route, other interesting cards (in addition to those I mentioned in my last post) include Enigma Sphinx and Foreshadow. After that, old standbys like Millstone don't seem too efficient. I dont know if this is any good, but it's totally unique.
MCD I think you have gone over too far to the opposite spectrum that Noble was at. Far too many lands/spells compared to the number of slivers. Sedge sliver while a powerful card puts a lot of tax on your mana base by requiring you to have a swamp and ample black mana out at all times. Why not go a little bit different route and utilize the most unique and powerful effects slivers have to offer, Gemhide sliver and brutally powerful 5 drop slivers. Sliver overlord, queen, and legion shouldn't be too difficult to cast if you have gemhides, city of brass, caverns, ancient zigg, and a full set of moxen in your mana base.
I know, my deck suggestion is rough. I don't think you can avoid running so many spells, though, because we do not have good disruptive Slivers. If they printed Tidehollow Sliver or Spellstutter Sliver, this tribe would instantly catapult to Vintage playable, imho. But, we don't have that. In the absence of a disruptive Sliver, I think you really do just need to go for the most powerful ones. I doubt you need much more than a single lord, maybe two. Once you have two lords and your board is 2 or 3 3/3 or 4/4s, what in Vintage is really going to stop you?
As for the mana strain, I don't think the swamp requirement is so bad. Tutor up a swamp, and then keep it open. The most common card killing slivers is probably going to be Bolt, and you won't see more than one of those per turn probably. One regeneration shield is probably plenty.
As for the 5-drop Slivers being powerful, sure, but they're also five-drops. Even with Moxen, you're looking at turn 3 plays, probably. (Turn 1 mox, land, gemhide is only 3 mana). I don't think bringing a Nic-Fit style midrange aggro deck to a Vintage tourney is a recipe for success, but who knows? At least it's doing something different from Merfolk.
