I think having towed artillery and morters would fix the artillery mechanics od the game. Towed artillery could be spawned at the HQ spawn points like tanks and other vehicles. Having towed artillery would allow teams and commanders to provide counter battery fire and really think about where to place the guns. Also it could allow for a completely different class of artillery team. Mortor teams would also be a great addition, working with the artillery team to hit targets.
Another thing that would be a great addition is to allow teams to play mine field before the game or let the engineers place it during the game. It also could make teams have mine Sweepers to clear out mines and other fortifications.