Given his relationship with Deep Purple, I see Iommi joining Ian Paice in Whitesnake in 1979; Coverdale is happy for a pretext to give Micky Moody the boot anyway. In a band with David Coverdale
and David Coverdale's ego, I imagine that Paice and Iommi only last for one album -- TTL's equivalent of
Ready an' Willing -- but that album would be
really good.
OTL, Whitesnake opened for Jethro Tull in 1980; if so, Iommi might patch things up with Ian Anderson, who probably seems sane, reserved, and modest compared to Coverdale (!). Coincidentally, Tull needs a drummer in 1981 after long-time drummer Barrie Barlow leaves the band; IOTL, that started a revolving door that included a short-lived gig with Phil Collins (!!).
A hard-edged Jethro Tull album in 1982 -- replacing OTL's
The Broadsword and the Beast, which is no loss as far as I'm concerned -- might even revitalize Tull and spare us two decades of mostly-unlistenable Ian Anderson vanity pieces.
Okay, so now Whitesnake finds themselves in need of a lead guitarist and picks up Vivian Campbell 2 1/2 years earlier than OTL, poaching him away from Dio. Of course, Campbell probably lasts no longer than anyone else does in Whitesnake, so in a weird convergence we still get John Sykes for the 1987
Whitesnake album that turned them into mega-stars.
Ronnie James Dio -- having lost out on Jake E. Lee to Ozzy and Vivian Campbell to Whitesnake -- decides to beat the bushes in the minor leagues before coming away with Dio's new lead guitarist: Yngwie Malmsteen (again, a few years earlier than their collaboration OTL).