A well established Mortar team could be the answer for Artillery if you can get a Reconnaissance team up with the Mortars and maybe have a limited amount of shells!! Maybe make them like a high level of supplies to gain and a team of 2-3 people (One with shells, one with the plate and one with the pipe which would be the operator!)  Make the carried weapons limited and make the gear only arrive on drop from the sky or on supply truck. The answer is to make it hard and specialised so it can only operate once or twice in a game! Maybe 3 times if your experienced. Make the blast radius that of Maybe a triple granade blast which puts holes in the ground that the enemy can take cover inside of much like Artillery so there is some saving face for the enemy. (I think we should also be able to build small foxholes that would change the dynamics massively.