From what I've heard second hand the WH Larps went fantastic! But I have to admit I wasn't there.
As for the BI's at most I think a 10% change is all that is being called for, if that. Really, it is pretty amazing that the core of what makes for a BI is still persuasive after all these years. I see the core as being that multiple tables are working on the same adventure. What I point out as the main difference between the BI's of past and the Arcanicon Delve into the Vault of Larrissa is that at the Delve PC's where able to go were they wanted, and fight what they chose to encounter. Thus everyone got a customized experience consistent with the choices they made. If they didn't like a particular encounter they only had themselves to blame, or perhaps the nosy PC idiot at the other table across the room.
Applying that to the Blessed Lands...
Say that city X was overrun while the PC's where away. The hero's then band together to go door to door and clear the town. The main difference from the Battle of Tanin is that the PC's get to chose how to enter and clear the town as individual strike teams. So functionally it would be run like the Vault of Larrissa. An alternative would be that the PC catch the bad guys entering through the tunnels under the town, and orchestrate a search and destroy counter attack before the town in run over. Pretty much any situation where the PC are on offense or a counter attack could be run this way.
I don't see that as a big change from the -players- side of things but it would resolve everything except the experience award concerns that have been raised. It would also mitigate the tenancy to pile on comments after the fact about a rough patch in writing since everyone had a different experience. Granted that is a bit more involved from the writer's side of the encounter and certainly more involved from a map-maker's side of things.