Pabely,
No one can deny Luton is best positioned and with so few homes around this site- south of the current location why shouldn't Luton be considered?
We have M1, M25, 4 train tracks and only 21 minutes by fast train from London west end.
The only thing I would change is re-aligning the 4 runways to 09/27 headings then Stevenage would no longer be direct under the flight path!