It's difficult to use factions with content on the way- we could put in a lot of effort only to have it invalidated when the dexes drop.
I took a look at the faction poll, but I didn't vote yet; I need to think about it. There are a few things that really interest me though, so here are a few ideas in broad strokes:
1) Whatever happens, I want to see the Inquisition involved. Specifically, I want an Inquisitor to investigate things with the help of other Imperial factions. At first, they would work with local forces, whatever those happen to be- most likely guard, and possibly a small mission of SOB. But once they begin to make discoveries (accumulate investigation points/ complete Inquisition specific Agendas (40k) or Tac ops/spec ops (KT)), they call in their Chamber Militant.
2) I LOVE Commorragh and Drukhari vs. Drukhari action. Like, combine the territories in the 40k Crusade rules with Bases of Operation in KT and fight over them in order to achieve a threshold which allows an Ascendant Lord to tear open a gate to realspace.
3) I love cults- both Imperial and other. Like maybe create a specific order of Crusaders, or a specific Death Cult in order to expand battle conclaves. If you just take Knosso Prond as DCA unit type/ character (ie. NOT a named Character), you've got two DCA units. Give Gotfrett de Montbard the same treatment and you're good to go. A few changes to the Cult of the Abyss keywords and unit options/ restrictions make a viable basis for an expanded Cults of Chaos option.
4) I LOVE the GSC life cycle. It's complicated though, because they reproduce to grow their forces and that can be... Difficult to handle with sensitivity. But playing out the life cycle of a Cult... It's something that I've been trying to get off the ground with the Chronicles of Saint Katherine's Aegis for years. Like, you can't include hybrids in an army until the purestrains infect humans who become Brood Brother fighters who also breed the hybrids into existence. Acolytes have to breed Neophytes. Neophytes breed the characters. Aberrants don't show up until the second cycle- ie. they are breed from the purestrain progeny of the 4th generation. Metamorphs show up in the third cycle.
And then they call the Nids, and their invasion happens in phases too.
So there are some thoughts. Actually voting? That's still a few days out. But maybe this can serve as food for thought until then.