A few issues which I don't think have been considered jump up here in my mind;
1. Initial problem is described as Depressurisation. Was it a failure to pressurise i.e. climb stopped at or below FL100 or even FL125 and then back to FL100 due to the cabin climbing? or Was the aircraft at FL150+ and the cabin depressurised, oxygen masks deployed? What was the rate of depressurisation?
Basically - can thre be people back there who could have medical issues because of the depressurisation problem?
That would make it a good idea to return sooner rather than later.
2. It appears that it is going to take 2 hours at low level to burn off the fuel to acheive a MLW arrival. Is there no suitable airport within less than 2 hours that the aircraft can land at as soon as it gets there?
3. Can the aircraft comply with the missed approach and balked landing climb gradients at the expected mass?
4. It is night. How long until daytime? What is the weather going to do in the next few hours?
These are issues that I would expect to be part of the decision process.
As for the runway lengths?
If the aircraft returns quickly then the full safety factor is not available. However, the aircraft will not be at TOW when it lands i.e. even an aircraft that takes off at MTOW, catches fire 10Kt above V1 and does a tight visual circuit to land will not land at the take-off weight.
The aircraft completed a safe take-off on the runway. Thus in theory, starting at the piano keys, it could accelerate to V1 and for another 2 seconds and then stop with one engine out without ending up in the mud.
What is V1 in relation to your touchdown speed? and where is it roughly on the runway? I would expect that V1 did not occur at or before the aiming point?
These are some of the factors that have to be considdered.
Having said all that, if the climb was stopped at 5000ft becuase the cabin was climbing with the aircraft and there is no other reason to return plus the fact that we are at an isolated aerodrome, I would be more in favour of waiting for the weight to reduce because anything else is rushing and putting money before safety.
To burn off the fuel, I would prefer flying long straight legs with only drag items that do not cause a lot of noise / bumping. This keeps the pax happier. It may take time - but they expected to be on the flight for a lot more than the 2 hours it is going to take to burn off the fuel low level(if that is not the case then how were you going to land at the destination?). Subject to SOP, they could receive an in-flight service and time taken to liase with pax and company regarding later flights.
Think of it like this -
Dear Pax,
I realise that you are not feeling 100% secure with the situation but there is no immediate danger. Would you prefer to;
1. Return for an overweight landing with possible dangerous over-run then (if ) we make it to the terminal, q at a desk for 1 hour to re-book and then sit on the uncomfortable terminal seats for 3 hours; or
2. Sit here strapped in for 1 hour with the noise and turbulence of the gear and spoilers extended before making a normal landing and q at a desk for 1 hour to re-book and then sit on the uncomfortable terminal seats for 2 hours; or
3. Sit here for 2 hours, have your in-flight service, watch the movie, let us have time to book your replacement flight and when we safely arrive back at the terminal, have 1 hour to collect your bags, check-in and proceed to the gate?
In each case the delay for the pax is the same but 1 has the added posibiity of never getting to the destination!!
In the end it is a Command decision. These are just s few points that I feel must be weighed up. There are no doubt plenty more and the longer one takes to review the options fully, the lower the landing weight!!!!!!!