First off for anyone who doubts the ability of arty to hurt Tanks I strongly suggest that you have not read enough about Kursk.
It was to be dead simple about it, a huge artillery trap for German tanks.
Yes making towed arty have to drive between bases would be IMO a good way around it.
Another would be to hard coad setup and traverse times so that it can't instantly deploy and fire on target.
Whatever we think its in Pyro's and HT's lap, and they have to be able to figure out how to integrate it into gameplay without balance issues before they will even consider adding it. This may be our addiction, but its their PAYCHECK, trust me, they take anything that could effect that paycheck very very seriously.