Would a refueling stop be cheaper than finding lodging for all the passengers? This is somewhat late followup question to my original question. Basic story was flight got delayed by almost 24 hours because first, technical reasons, secondly temperatures were very high.

As far as I can see airlines had to accommodate all the passengers somehow, either in terms of hotel rooms and meal or on other flights. There are costs involved in every action.

If they had taken off Abu Dhabi on less fuel and then refilled somewhere else would it have been cheaper? Would such refueling stop be allowed where passengers are not allowed to get off? Just fill her up and continue.

Without knowing any technical/legal/contractual details, my simplistic view is, you land at some airport around 6 hours away, fill up your tanks - might take around 1 hour and continue rest of your 14 hours flight. Your crew could be in time limits as they must be provisioning for full length of the flight plus possible diversions, moreover almost working as planned and you don't have to pay for hundreds of rooms and/or rebooking/re-routing costs of the passengers.
I don't know what aircraft you flew on over 3 years ago. The current options from Etihad are Boeing 777 and Airbus A380. The route doesn't seem to be nonstop anymore, aboard any airline.

Along the shortest distance -- great circle route -- there aren't many options for an A380 to land and find support equipment mid-route (shown below). Refueling can occur with the passengers on board, there is a procedure to be followed, which includes alerting the fire service at the airport to be ready.

If we take only the cost of fuel into account, and a 777-200 as a baseline, actually stopping every ~6 hours is more economical. (This doesn't take into account landing fees, accrued cycles*, passenger convenience, etc.) Not just for your flight, but any long-haul flight; the fuel burned to carry the fuel for long distances becomes considerable after a certain range.

Another consideration is which freedoms of the air, say Etihad/UAE, has with say Russia. The second freedom specifically is:


  The right to refuel or carry out maintenance in a foreign country without embarking or disembarking passengers or cargo.


While they are called freedoms, not all country-pairs mutually allow all the freedoms. The specifics are usually not public and are contained in the air service agreement between any 2 nations.

In all, it might have saved fuel even if we included a detour off the great circle. It certainly would have increased the maintenance cost. And it would have been an operational nightmare to arrange compared to a hotel and meal.

* Pressurizing and depressurizing twice, applying the takeoff thrust twice, applying the brakes twice, etc., all increase the maintenance cost.

Re: comment about London or Sweden already being destinations:

Already having flights to Sweden, UK, or Italy, doesn't mean the 2nd freedom is guaranteed. Note that "not many options" $\neq$ none. The middle half of the flight is either over tundra or the Arctic Ocean. An airport like London Heathrow won't welcome an on the spot request for a slot; busy airports in Europe are running near max capacity, so unless it's an emergency, on the spot slots really aren't realizable. Three daily slots to land at London Heathrow (as a destination) already cost Etihad £46.2 million back in 2013.


(gcmap.com)