Scouts are easily destroyed in the endgame (therefore a high risk of investment), and time is often more valuable then economy (assuming both players have relatively similar strength economies) at that point. Also, if an enemy gets a titan much earlier then you were expecting (say they get a strong early game feed) then you will have little to no early game counter to slow down the inevitable destruction(from what little we know about rebellion).
It might be easier to set a feed over time limit in multiplayer. Feed is the least skill based way to help someone and it is also the second strongest way to help someone in multiplayer(the primary being full military support). Early game feed is exceptionally beneficial and I would argue that a feeder giving everything to a military based player to rush to titan would most likely become a popular online tactic. I think this would be very discouraging to online players who are new to the game as they would literally have no way to defend against this sort of tactic.
Limiting feed amount and highlighting the importance of micromanagement (which is already being done in rebellion via capital ship buffs) would be a way to ensure that feed won't be abused.
Well, there's a few catches with all this. One is that we're just making up guess work concerning the Titan's abilities. It might not be terribly viable on its own much less mobile enough to crush an enemy with enough speed to stop them from building one.
And another thing is that the original question was about the survivability of a Titan in a mine field. That's still not really known, especially since you would have to go through a lot of minefields to defeat a competent player.
As for scouts, I was just answering the question of how to deal with mines should they pump them up in power and the AI go crazy building them. Even if scouts have no survivability, it's better to build a bunch to suicide than to let your fleet go in blind and they take the damage.
As for late game feeding, I can't say I know how that will work out. It goes back to the questionable strength of a Titan. I mean, if players in a 3v3 can put up 3 starbases at a bottleneck and that alone pulls the Titan under, then the two teams just have to see who can pump out better support fleets. Then again, feeding can backfire if one team is quick to kill off a weak feeder. I dunno.