All, it seems to me, the modern day low cost carriers introduced was one-way fares, before then one-way fares were extremely expensive so of course "we" would regularly buy return tickets that included a Saturday overnight and, if we weren't going to use it, we'd throw the other half of the ticket away.
But these low cost carriers aren't necessarily cheap, an ex boss of mine, we were mid point between LTN & BHX, she had friends in the city of Belfast and she swore blind travelling "orange" LTN/BFS/LTN even though I pointed out to her that it was actually more convenient and cheaper to travel "BACON" BHX/BHD/BHX.
I regularly had business in FCO and MXP, from BHX Jet2 did FCO and FlyBE did MXP but it was actually cheaper, and more convenient, to travel via ZRH (an hour (ish) in ZRH in each direction) and on each of the four sectors one got a complimentary snack, coffee, beer and Swiss chocolate ... and one could buy duty frees routing non EU!
So I'm not a great believer in these, supposed, low cost carriers and if it were to go back to the way it were before them, i.e. those cheap Saturday night returns, I don't think that would be such a bad nor expensive thing.
These days I own and operate a small resort, here to eat out (BBQ chicken & rice) can cost less than one GBP ... I have guests coming to me expecting to use our restaurant kitchen (free of charge) because they can't afford to eat out ... I'm sorry but these people should never have left home and I simply cannot understand their mentality that they are taking a holiday that they cannot afford to take!
The OP has hinted at less than desirable "safety" standards ... Well I'd suggest going back to the old days whereas it was aviation professionals running the airlines and not the beancounters, a beancounter understands diddly squat about safety, they only understand pounds, shillings and pence!