(I feel I saw this request a long time ago, but I wasn't able to find it via forum and google search. Sorry if it's really double)
In my opinion it's fine tech-stop routes have a ticket price disadvantage and PAX prefer nonstop flights.
But why tech stops need 100% of the turnaround time? The aircraft must not be cleaned, there must not brought new food to the aircraft etc. It's just refueling and maybe a short check by the pilots if still all engines are attached to the aircraft.
Due to this it would be nice if the turnaround time for tech-stops is reduced by 50% and rounded up to the next five minutes, so for example 737-200Adv has 35 minutes turnaround-time, at a tech-stop it would be 20 minutes. (35/2 = 17.5, rounded up = 20 min). No big contribution for this aircraft, but a 747-200 would save a whole hour.
The shortage of 50% would not be boost tech-stops to be overpowered, it'd be just a little increase. On the other hand it would increase the feel of realism.
I also don't think it would cost endless coding time. It's just half the current time + maybe round up (as it is done already as far as I know for each flight).