I have made a fair bit of progress with this. I've created a system that makes it fairly easy for other mods to add new holocrons without requiring extra compatibility patches. I've achieved this by pacing acquisition of the holocrons similar to the lightsaber and Force forms, so which holocrons you receive depend on your character progression, rather than the order in which you visited the planets. The Disciple has reactions for generic Jedi and Sith holocrons, which would grant a random Force power or Force points similar to the dark taint in the Tomb of Freedon Nadd. My plan is for the base mod to include four Jedi and four Sith holocrons (i.e. three of each group of holocrons will have unique reactions and one will have the generic one). Any holocrons added by other mods would add to the count of generic holocrons without breaking anything.
What remains is to:
Copy the same changes to the Disciple's Khoonda dialogue and modify it for the version with him there. I didn't want to do that manually, so I stopped working on it until a better option was available, and I think I have a good idea of how to write a tool to resolve this now.
Finish the holocron models. I started some, but I forget what state I left them in.
Implement cutscenes for examining the holocron, both on the Ebon Hawk and on Khoonda.
Place each holocron and implement the discovery cutscenes.
Finish the Disciple's Jedi training dialogue and implement the cutscene for it.
Get multiple people to test the game.
I also of course plan to design the mod to be compatible with any male Exile & Disciple mods such as Party Swap and Handmaiden and Female Exile - Disciple and Male Exile Romance without much fuss.
As I said in the K1 thread, I have a WIP thread here, but it's out of date. The gist of it is that lightsaber color crystals as they function now would be replaced with items that include both a hilt and a color crystal, which you can assemble with different hilts and colors to change the final model that is rendered in the game. This is a design a few other mods have executed, although I think what makes my implementation different is that I figured out how to do it with minimal computer terminal dialogue.
The K2 mod would have to be a little different from K1 because it's not possible to give every character a unique design, both for technical and thematic reasons. Technically, there is a limit of how many lightsaber models can be added to the game. Every color counts as a separate model, so there are trade-offs with the number of distinct hilts one wants to provide and the number of colors that can be made available for each hilt. Thematically, the game does not provide any "canon" lightsaber colors for the player or party members, and it feels wrong to me to lock most of them into specific hilt designs with that in mind. The up side of not assigning a distinct hilt to each party member is that hilts could then be available for any color.
Regardless, as in the K1 version, other NPCs like the Jedi Masters would have unique hilts, and there would lootable lightsaber items with unique hilts, such as Freedon Nadd's. There would also be "material" hilts that could be crafted by finding rare items throughout the game. Maybe the player and party hilts could be handled by providing more of those options.
My priority is to finish the K1 version before moving on to K2, but I would welcome any contribution for either game.