I hate modders-they really piss me off. They suck at playing the actual game and wait for developers to release the game files so they can further manipulate them instead of them getting together-build a game and make millions, build a mod silently and apply for a job at iron clad.
Modders can be very valuable for a gaming community, allowing games where interest might otherwise fizzle out to have new life. Maybe it's more relevant and valuable for FPS games than RTS, but modders' efforts shouldn't be discounted. They essentially increase the value of the game that you own because they are providing you with free content.
Right now mods aren't very viable for online multiplayer PvP simply because so few people play online. However, it's conceivable that if Rebellion were a big hit and thousands of people played it online that mods might become viable for PvP.
What if someone developed a mod that encouraged people to log on and start playing real games? The right mod could be beneficial to the PvP community in various ways.
Also, consider the possibility that we might need a mod to improve the PvP game. Suppose that the addition of the Titans (or Corsairs, etc.) isn't good for game play and we wanted a mod that just removed them completely. It's a modder who would make the mod for us.