It's getting clearer Hangar 6 would have been a terminal. This is, according to a Labour spokeman (Tommy Bruen?) on Morning Ireland, what everyone up in the airport thinks (fears more likely).
It's perfectly placed as a terminal, probably just need buses to get people to the planes.
If Ryanair could open a terminal there a couple years down the line, then they could easily absorb the higher costs of operating here for maintenance. Even if they eventually moved that maintenance away from Hangar 6. RA could easily guarantee hundreds of maintenance jobs if they could get the low cost terminal, since the terminal savings would dwarf the maintenance salaries.
I'd guess the hangar could be turned into a terminal for a few 10s of millions, so it would pay for itself within years and possibly just months. Quicker than the intergenerational costs of T2 at least.
So Ryanair's side is pretty easy to understand. Probably would even admit if directly asked especially now that the game is almost over.
The DAA's (+FF) defensive move is also simple, they've no chance of T2 paying for itself if Ryanair avoids most of their charges. They'd prefer Hangar 6 knocked down than used by Ryanair.
What's not so clear is why Aer Lingus are playing along with the DAA as if they were still both tied at the semi-state hip. My guess is the DAA are effectively paying them to use the hangar (e.g. offering them a cheaper rent for hangar 6 than for the smaller hangar they moved from).
