Having read through the thread so far, I have two comments:
1) Wrye Bash and BAIN installers/BCF files seems like the best choice for you, over OBMM, because of your OCD. The reason is the function which lets it track when a mod overwrites files from another mod, and automatically restores the original file when the later mod is removed. For example, Arthmoor has made a whole series of village mods, which include updated scenery paintings used elsewhere in Oblivion, to reflect the changes his mod makes. When the village is removed, Wrye Bash will restore the original painting.
2) Be careful when adding larger "additional quest" mods, as they MAY not be "idiotproof". Some mods define the conditions where they will begin carefully, and are thus easy to integrate into the Oblivion experience. Others may not do so well, and assume your character is at a higher level than they are, or even has completed the Main Quest, when they are in fact just starting out. That additional bit of checking before installing a mod may save you a lot of mental stress when something "doesn't fit"
On a similar note, I would recommend SM Plugin Refurbish in addition to the official DLC files. It adds delayed starting conditions to them all so you don't get a heap of immersion-breaking information suddenly dumped into your game journal. Adds to immersion, and doesn't make the content seen inappropriate. It also works with some of the expanded/extended DLC versions from the modding community. (I tend to class any mods which help to make the game world more believable for me as "immersion" mods - there are, of course, myriad different ways to define "immersion".)