PT,
Much would depend upon the capability in track capacity, sensor range etc of the smaller platform. Also, crew coordination between the different sections would be more difficult by having 2 platforms. As for training.... All the consoles in the E-3 are identical - the console is programmed to carry out a particular function on the aircraft, so you could have 10 weapons controllers on the aircraft or 10 picture compilers as required. The problem is maintaining the training and currency of all the weapons controllers. Multi training is perhaps the ideal, but if the assets are not available to train then maintain competency then too many can be more of a hindrance than a help.
At the end of the day, the controllers require a recognised air picture to carry out their tasks, and a mix of crew specialists on one platform is the most efficient way of achieving this.