TopBunk.
The answer to your last question is...legality, plain and simple, considering FAA requirements. May be permissable under JAR.
That would be your problem.
FlapsOne
Just for the sake of discussion...
Why would you, assuming you were the Commander of a longhaul flight from (for example) KUL inbound for LHR, overfly suitable enroute alternates KNOWING you would have too little fuel upon arrival to divert, never mind hold?
In companies where I have worked, the Chief Pilot would take a very dim view of such proceedings, and with good reason, IMO.