Dude, half the things you want is not even possible :
There's a max amount of regions in RTW, and that is 200, sea included. Hundreds of thousands population is also pretty impossible on RTW or MTW2 -> revolts, population decrease with perhaps 15%, probably CTD's , etc... And how will you divide them ? Heavy scripting and coding ? I'm pretty sure it's impossible if even if you were the best at both things. And how will that civilization thing work ? the closets thing i can see is religion in BI.
Again, you don't seem to know the hardcoded limits of RTW. There's a reason that no mod whatsoever has more than a max of 242 units. 242 Units is the max you can have on RTW. Graphics bringing par to MTW2 is simply imposible, it's another "system". The best looking units for RTW are found in RS, LOTR-TW, CATW, and Blue Lotus. And even those aren't really the same level, and they are made by the very top of the modders. And even if it would work : 322 units with MTW2 graphics on RTW engine = extreme lag. Perhaps 3 framerates per second ? RTW doesn't make use of multiple cores, so even the best systems wouldn't be able to play it.
Seeing that you don't know all this, I doubt you'll ever be able to make this mod on such a scale, all by yourself.
i'm really sorry to bring you down like this man, but it's reality. No way to get around that
