Scott
Parallel runways should add to your ability to get aircraft in and out. Unfortunately, if your airport operator has pandered to the demands of the public to get their new runway built and agreed to ludicrous noise abatement procedures then that ability will be much tempered.
And as for allowing mixed mode...they'd much rather have VFR aircraft going around in circles for 10 minutes waiting to land on the arrival runway, rather than allow it to land on the sometimes unused departure runway.
Logical? No
Political? Yes
Bull!!!!? Absolutely!
Oh and back to the thread. Two runways at Luton. Once the first one gets near the capacity of a "proper" runway, i.e. taxiways to both ends, maybe then they could think about it.