Without spoiling any tech that isn't already posted here in previous seasons:
I think Fastbond was banned because of Turbocat: Savannah, Steppe Lynx, Fastbond, Selesnya Sanctuary = T2 kill
In a creatureless format it's fine. Even with creatures, this is much more easily disrupted than other combo.
Leyline of Singularity was banned because of the Karakas combo, which matters less in creatureless.
Dark Depths, Thespian's Stage, Urborg, Tomb of Yawgmoth makes an uncounterable indestructible instant speed 20/20 flying on turn 3. It's 1 turn slower than Hexmage, but there's still space for 1 disruption slot. Without seeing how the format shakes out yet, that seems very hard to beat.
Elixir of Immortality was broken in other seasons and became a late addition to the banlist. It was banned for its low requirements to recycle compared to other engines (made it a flexible fit for many decks) and because it has a solo-combo of +5 life per turn (which many decks can't beat). In a creatureless format, Elixir seems even more busted.
Channel is also easily abused. Not as bad as T2 Emrakul, but you can still basically win turn 2 OTP.
Force of Will was a meta choice. In other seasons we allowed both Force of Will and T2 combos. Later we banned both Force and T2 combos. I think you can't have one without the other. Force is necessary to police fast combo. For a creatureless bannathon, it seems fine to have both Force and fast combo.
Flash, Mana Drain, Leyline, Fastbond, Mana Vault, and Time Walk all seem fine to unban.

