Basically, I feel this game lacks the lifetime we would want out of a $60 game while still having really good base mechanics. To help combat that, I suggest a longer, larger scale, more strategic gamemode. I think it would be cool to see maps that are spread out, having 2 castles on either side and a battlefield in the middle. Along the map it would be 2 or 3 lanes with multiple sets of points, 9 total or even 12. The concept behind it is that you cant capture a point in a further line without having all 2 or 3 in the current line. To make it feel even better you could introduce 6v6 or 8v8. When one team reaches the other castle some levelolution could come into play with catapults and siege towers, and when the courtyard and battlement points are capped its game over. I think additions like this that improve the overall scope of the game can really add to its lifetime.
Try these on for size:
"Between a Rock & a High Place"---environmental gauntlet
"Battlefield Siege"---the competitive siege scenario
"Defend From the Cannibal Throng"---the survival siege scenario