Not if they're implemented like APCs in which you just sit in a passenger slot.

Well if you look at how the Titans are now. They are like choke points that gathers a lot of people together. To me that is what causes the lag. A congestion of combat with a lot of different pings. I might be wrong on the reason but it seems right to me.
As for the movement. Titans do not move fast enough to cause problems to the players. So how would changing it from the way the look now to say a Star Destroyer or Corvette change that fact. The over all design would be different like hall ways and rooms; plus how you enter them. That would be the hardest thing to do. It would be adding a totally new object to the game and how you would make it work in a feasible way. That is why I could see it being some time before we see this game mode for this MOD. Got to take it one step at a time. I can wait.