To be honest, I don't like most of these latest suggestions about titans.
Ground combat needs improvements compared to the current situation. That's undeniable. New units needs to be added, new mechanics too. Probably, a complete redesign/rebalance.
However, a lot of the suggestions I see in the last two pages or so aim to make titans something else. Something more complex and probably hard to code and balance. Something, plainly put, that is not just "another ground unit".
I am not saying that something like that cannot be implemented. However, that is only AFTER ground combat has been revamped and we know more of how the new ground combat is going to work. Until that happens, there's no sense in making "movable PDCs". How would they work, interacting with normal troops? Having anti missile capabilities. How would that be balanced, against normal troops?
All these changes can be discussed, weighted, implemented only after ground combat is overhauled into something that can actually support all this. Until that happens, titans should mostly be normal ground units to preserve balance and coherence across the board. The extra bombardment attack they have right now is just about the limit of what I would consider an acceptable advantage over normal troops, with the current rules.