Parkway station is completely the wrong side as well to it and that would render that practically useless.
Ah, but....any new terminal(s) to the south of the existing site would be served by a new Luton Airport Station on the adjacent railway line, with a direct covered walkway/people-mover/travelator into the terminal(s).
The existing Parkway Station would no longer serve the Airport.
The platforms of the new station would also be long enough to take all Midland Mainline trains instead of only its 'Meridian' services.
Don't forget also that Abertis (one of Luton's new holding company's partners) builds and operates major roads in Spain and so construction of the required road links - subject to planning approval - would not necessarily have to wait for the local councils or the Dept of Transport to get off their ar**s!
We're not talking Luton Borough Council fag-packet designed piecemeal development here - we're talking big-time strategic thinking by a world-class company whose operations in Spain alone, put BAA firmly in the shade.
What you see at present is only the interim arrangement...