So many people are probably asking:
Why am I even wanting to do this?
Well for me everything since 13th Black Crusade has been like "The man in the High Castle". Without sounding like a washed up vet returning home from 'nam...
"You weren't there man, you didn't know what happened".
13BC was my Vietnam (not trying to diminish the conflict and the virus bombing/war crimes).
The travelling, the physical loss of an army which I never really recovered from (my Eldar) along with the BC hype from GW in WD and online.
For me, Cadia still stands and Eldrad is f knows where after fighting a BSF on his own. The timeline should continue from there with Chaos beaten back and licking it's wounds while the rest of the galaxy breaths a sigh of relief.
I'd like to advance the storyline from then, fluff wise I could blame everything on the warp causing some kind of literal split in reality with on one side Abaddon is defeated and on the other he isn't.
I agree with many that GW had kept the timeline stagnant and that something eventually had to give.
"Ohh look guys it's ANOTHER black crusade" - Everyone on Cadia.
Seriously it was getting like 'Midsomer Murders' in there, same stuff every few years. It needs change and frankly someone competent should be in charge and the huge amounts of potential it seems GW couldn't be bothered to use sitting in a disused toilet in the corner of some dusty Necron Monolith presiding over some flint/stick based backwater shithole planet waiting for the local Indiana Jones to fuck everything up for us.