Can't we keep PDCs? Frankly, I don't think anything but a truly long range missile capability is going to discourage glassing ground troops instead of trying to dig them out.
Beam armed ground troops seem improbable to me like titans. A several hundred ton heavy weapon is not easily moved around on roads, and is very conspicuous and vulnerable unless it is deployed in prepared, hidden and preferably armored positions, which is pretty much the description of a PDC