If Vampire is retracked, I could see them going for the Vekoma SFC-style hardware, personally.
It’s very well proven hardware, with numerous successful installations worldwide, and Vekoma have worked on Vampire before.
Compared to the other options, Vekoma seem to me like the most compelling option.
While S&S are technically the successor to Arrow, their only family suspended coaster, Merlin’s Mayhem at Dutch Wonderland, was pretty problematic, and the company has little experience with that style of coaster aside from Merlin’s Mayhem.
While Taziker have worked on Arrow coasters before, I’d wager that the recent issues with the Colossus retrack at Thorpe Park may have put Merlin off doing work with them again, and in the event of a “big bang” retrack, Taziker also wouldn’t provide the sort of technical overhaul that the ride would hopefully receive alongside the new track.