(Dang, see a lot of good ideas here) Mine would be this: Computer generated tanks/enemies/allies. Much like in the tutorial these would be none player tanks who act with pretty simple methods. The idea would be these could be utilized for special kinds of battles. I would suggest that they still possess only a little skill, more then in tutorial but still not equivelent to a good tanker, but that they either have large numbers against you or higher quality weapons and hulls. This mode could also be utilized for clan related battles, imagine a sort of quest that has to be completed with a team to reasonably succeed but has a very high reward for everyone involved. My assumption is this won't get used due to the requirements you'd have to put into it, but I wanted to offer it anyway.