Dispensation

Sound assets can be packed into an uncompressed BSA, just not into a compressed BSA.

It has to be moved or reinstalled outside of it.

Oh that is perfect, thanks! By the way, my Oblivion files were obtained through GOG rather than Steam (ES I - IV were on sale in a bundle that was too good to pass up). Other than the data file location, is that going to matter? GOG or Steam doesn't matter.

I have an up to date guide in my signature, if you want some mod recommendations.

It's good to see Oblivion's still getting love from mod creators.

Only one is Enhanced Economy.

That mod is Migck's Miscellaneous fixes tweaks and additions.

The only mod I know that adds new dukes is Shivering Isles - New Dukes. Your second request seems very difficult without causing issues or bugs, it would be a lot easier to simply create a new seperate questline.

Read the MOO PDF, you can use a blank WAC.esp to let MOO distribute things from the ESM.

For the latter try Oblivion Upscaled Textures.

Maybe a bit dated for a mod. MOO lets you play a different version of WAC as well.

It's under cancel button.

Lost Boy Cavern has a unique boss and a non-journal quest.

Wrye Bash is considered the best for Oblivion. If you don't like that then Mod Organizer 2 is a second option. I wouldn't use any other mod managers than those two.

That mod is called 'Legacy of the Dragonborn'.