Thank you Grasscarp...
If it's public transport, it's written down in the JAR-OPS Fuel Policy in your Ops Manual Part A - possibly Section 8, Ops Procedures:
Read Alternate fuel which shall include...
The general object of the standard JAR Fuel Policy is A sufficient quantity of fuel is carried for the intended flight with a safe margin for contingencies
What your suggesting is the Account's Department's/bonus driven management's dream but I would suggest not legal! Even in a private ops environment, I would be amazed if any pilot would except it! YOUR fuel policy would significantly reduce ANY margins of decision making for a Flight Crew now 'boxed' into a corner - simply not realistic for London TMA Ops. Remember that wonderful weather day, I think Summer 2009, I was inbound to LGW when ATC at LHR had evacuated the Tower due to a fire?!? It was carnage!
In my previous airline, we nominated LHR as the alternate for LGW, this was subject to an agreement from NATS and only used in times of good weather and very few carried PLOG fuel!
The fact you can't see a problem would lead me to believe you are:
*Finance/Management/Owner (*Delete as applicable) Sorry it's harsh, but as a pilot what you're suggesting is tosh!
Cheers
JB