Good question vipero - and well put.
A Captains view here:
The rules are designed to prevent an aircraft running out of fuel because destination and alternate weather are out of limits. It nearly happened to me in Cyprus some years ago when two airports fogged out at the same time and it wasn't forecast.
Our (Jar)Ops manual says:
'Met reports and/or forecasts must indicate that the the weather will be at or above the applicable planning minima' for the specified time period.
'If planning minima is not fulfilled, two destination alternates must be selected.'
On that basis it would be legal to dispatch if the criteria are met. I had this recently when the the destination Met Office was shut. We carried round trip fuel which satisfied the criteria. Also we filed (at least that is what I was told) for the first alternate where the weather was OK and then diverted. Paperwork exercise really.
Now . . . To the culture and legality of the decision making process.
The legality for the flight rests fair and square with the Captain. Some of the rules deliberately have grey areas and that is where the Captain will have to make a safe judgement and decision which cannot be overuled. I have not yet read an AAIB report where Ops personnel were cited.
If Ops say you can go and the Captain says no then the matter is final. You can replace the Captain but the next geezer might say no too.
Correct me if I am wrong but in the USA Flight Dispatchers hold a license and may have some authority. That is not the case in the UK and therfore ops must be considered as an advisory service.
An airline cannot (legally) undermine the authority of a Captain to make a safe decision.