I have a feeling loads of people are going to post here telling you that RTW cannot be modded compared to MTW, so I'm going to put in my 2 cents first:

RTW has some things hard coded which would have been possible with VI, like new factions, but it also has some things wich couldn't be done with VI, like projectiles.

I think it would be unfair to judge RTW too early, modding MTW was opened up thanks to VI, I wait till an expansion, then we'll see.

This post is shorter than I intended, as I have to go now.