Thank you so much for responding! I really appreciate it and all the work you do!

I guess part of it is that I really loved the "Blood of Azog" expansion of that Pass a bit more upward and was sorry to see even those newish elements were still carved-off by the avalanche in the TA 3019 version. I get it though: that quest with those Orcs has been long in place with the avalanche.
I do have an idea for a work-around you could consider: What about a set-apart "instanced" area like Zirakzigil? It wouldn't be large or extensive. I am thinking of the books you have us click to enter the older Azog version of Dimrill Dale. You could even consider simply expanding on the current Moria Zirakzigil map with winding, narrow paths up and down the mountainside to do this.
The idea is this, to get-around the time-locked problem while keeping all storylines intact: what if an NPC in Erebor gave us a quest to see if the Redhorn pass is open? As a little gag, in this concept, you'd place an actual red horn on a pole that you right-click-on (like a summoning horn) just below and out of view of the avalanche site before advancing forward. This new, small "instanced" area would then be named "The Redhorn Pass of Caradhras," (or would simply be part of the extent Zirakzigil map) and it would include the traversible copy of the new Azog area expanding on the pass, and it would include the vale that Tolkien describes that we see just below Zirakzigil from the Moria map, and after crossing that, we would click on the "Redhorn clicky-object" on the opposite end, opening up the pass and completing the quest on the Eregion side. Maybe its to send a message to the Gemcutters we met with the Grey Company or something
Of course, this instanced area would also get us between the "Rhovanion" and "Eriador" maps with the clicky-objects acting as "enter / exit" waypoint portals on either side.
To get back and forth, then, all one would do, after completing the level 130 quest, would be to just click the Redhorn clicky-object near the top of each side of the Pass. Could throw some challenging stone giants to hurl stones and more frost grims and goblins to make it exciting in the middle!
But, that would be what I'd think of as a fair balance between respecting the story / time-locked nature of an area while also opening up some more possibilities. By making it a level 130 quest, a below-cap person could not pass through the Redhorn, the story contiguity would be maintained, etc. Meanwhile, opening up the pass for level 130+ players by means of a separate instance unlocked with a quest would also make Galadriel and Celeborn's eventual return home by that same route make some more sense, and it would also really help with the current storyline in Black Book with Gandalf taking Isildur's remains back to Rivendell also
Anyways, that's just my creativity on a roll there- feel free to take it or leave it, I certainly understand

I very much appreciate the next forthcoming portal out of Gundabad for landscape contiguity!
I also want to just thank you so much for all the awesomeness you've done to Dimrill Dale, especially on the Zirakzigil side! Those views of lands stretching down to Fangorn are amazing! I also really hope you'll consider finishing the trail of the new Great Way someday, into those lands we can see now; it would be very cool to follow the Misties from Dimrill Dale southwest along the mountains to the western sides of Wailing Hills, Limlight Gorge, Balewood, and Entwood eventually
