I'd guess I'd advance the timeline.
It's the most logical way to link the FR now with the FR to be.
I'd just not have done it the way, ummmm, they chose to.
When I read the Grand History and got to the Helm/Tyr/Tymora Love Triangle Plot a Mexican Telenovla would be embarrassed to use, I knew my FR days were finally over.
(I kept hearing chants of "Jerry! Jerry! Jerry!" while reading it. This was the winner of the Dumbest thing I've ever seen in D&D. Miniature Giant Space Hamsters & the Volo novels I now consider the "Good Old Days")
If you are going to kill off dieties (I don't mind Tyr, Norse God getting the boot, just the execution method was cruel & unusual). Why have you got to kill off the good ones?
Helm I really liked, he'd really managed to get a unique FR feel to him. Could you kill off Cyric already? Next to Adon, he was the most whiny character in the Avator Cycle, and he still pales next to Myrkul & Bane.
I'd have been willing to advance the timeline far enough to let the new System meld into the Existing one (5-100 years depending on the depth of change).
What I would do.
I wouldn't dumb it down to the level the most incompetent DM can't screw it up. (Which, at present seems to be what they MIGHT; Might; be attempting).
Some of the Problems they are "Fixing":
1. The lack of Danger in the FR (Points of Light).
Of the Hundreds of Games I've ran & the countless more I've played in (under decent DM's). Number of times I've had this problem. Zero. I find the Mercantile/Trade/Diplomacy Game has an endless number of plot points which a true "Point of Light" kills dead.
2. The UberNPC. Elminster saves the day! Again!
Again. Never once had that problem. My adventures are for PC's not NPC's FR has enough stuff going on that there is plenty to go around. However, when my PC's get 15-20 level its nice to have the Stick of those Uber PCS to keep them from doing things like trying to take over Waterdeep.
I have played in games where an UberNPC does everything for the Players. That was always cause the Module Sucked or the DM did.
From what I've seen, I don't like where the FR is headed (nor a lot of 4th ed).
But, I'm withholding final judgement until the Final Thing comes out (anyway, most of my games are now in my own homeworld, I get FR stuff more out of a sense of habit than anything).