What realism mods should I look at while taking FCOM into account? I want the real hunger, thirst, sleep, and fatigue ones, are any of their functionalities already included? What other immersion/realism mods does anybody suggest?

COBL versions of Real Hunger and FF_Thirst, plus Realistic Fatigue and Real Sleep Extanded works for me. These things are not included in FCOM.
For more check Delte's Immersion thread.

I use Simple Essentials for hunger/thirst/sleep, and use tons of other mods that tweak things here and there (Phitts Phighting Phixes, Deadlier Creatures, DukePatrick's Combat Archery, OMOBS, AN-Real Lights, Duke's Actors can miss now, Actors Care, kuertee's many mods). And I love my game! Thank you modders :foodndrink:

Yeah I just found Delte's thread and have been downloading like crazy lol. I'll probably wind up breaking my game again XD. I have so many mods now that I actually think I'll have to pick and choose which ones make it into my final cut lol. I always grow bored of Oblivion and the reason is a lack of realism, immersion, and true roleplaying opportunities. I'm going to revise that now. Thoroughly. Thanks guys

Delte's thread is great for immersion lovers (that includes me), but it hasn't got updated much in the last year or so, so some of the advices are quite old. If you look through it, you'll find a post by me listing newer and better alternatives to a number of the mods there