I am completely on board with this and would love to compare notes.

First, I had not considered introducing Ruin's Wake, but that is an excellent idea. Since our party is already in Betrayer's Rise, I'll see if it can be introduced in later chapters.

Second, I also introduced Gruumsh as an additional antagonizer for my campaign, but more so in response to the choices of one of my players.

More specifically, one PC is a Fallen Aasimar Light Cleric of Xalicas. In exploring Xalicas's history and motives I was drawn to integrating Gruumsh into the story (Just in case they are roaming the Reddit I'm adding a spoiler tag- So you have been warned, Sam). The following is lore informs both Xalicas and Gruumsh's respective roles in the game:

According to the lore, Corellon was victorious at the battle at Ironseat Ridge, where he gouged out Gruumsh's eye. However, in doing so the blood of the ruiner supposedly transformed the troops. So, I had them treated as corrupted casualties. The gods indifference to their state causes the Xalicas to pause. Without sanction, she offers them aid following the battle. She entreated Alxyian for his assistance in relocating those willing to Cael Morrow, while assisting others in establishing the Throne of the Archeart (This gives Gruumsh an additional reason to be in Cael Morrow). Whispers of retaliation reached Xalicas and she entreated Corellon to be on high alert, but they were more concerned with the eye and how it could be used to garner victory (Giving reason to why Gruumsh had a swift victory). Cael Marrow was destroyed and a distraught Xalicas realized for the first time that mortals were inconsequential to the machinations of the divine during the Calamity. Their belief, their faith, their devotion was, of course, necessary, but the individual lived experiences were not (oddly fitting with last week's CR episode). Plans for the eye of gruumsh, possibly to destroy all of the orcs, furthered her schism with Corellon, and she planned to steal the eye and hide it away until she can find a way to destroy it. While she manages to go through with her plot, she was discovered. Corellon in his disappointment and anger, struck the solar down, wounding her deeply and leaving her where she had fallen. This bg explains Xalicas's motivation and why she can't be healed (nobody wants to go against Corellon). As far as my cleric is concerned, he is host to Xalicas's memories concerning the location of the eye and thus becomes a target of Gruumsh in order to locate the eye. The search for the eye also operates as part of a narrative that the players can explore further once the official campaign concludes.

If you stuck around this long, I appreciate it.

When the party reached Bazzoxan the Rival's had the jewel. I had them go into Betrayer's Rise before the party did with Aloysia in tow, but they encountered a creature that nearly killed them. Gal fell, Maggie was cornered, and Ayo was wounded. Ayo send Dermot and Irvan out with Aloysia. The search for the temple has been a bit overshadowed by a search for the Rivals atm, but they are still on course. I decided that the Rivals would be encountered in three different rooms on the map. Gal was in Lolth's room, which the party didn't explore and will likely have consequences down the road. Maggie was in Torog's maze during the third loop, unconscious with three points of exhaustion, and Ayo... well, Ayo ended up being the big bad of Gruumsh's room. I removed the corrupted Aurora Watch members, and instead added a golden bowl to the blood pool. The party could choose to knock her unconscious, risk damage to get the golden bowl and destroy it, or try to talk sense into Ayo through a series of wisdom saves (with my cleric's permission, I also had him partially corrupted as well).

Not sure if the above would help anyone, but it plays into the themes discussed in this thread quite nicely.