In dota 2 it seems like half the games end prematurely because someone leaves, I'm not sure this is a good idea
Anyway, safe to leave wouldn't work with LoL because surrender exists. Riot's ideology dictates that it's "better" to pigeonhole people into games rather than preserve the freedom of the individual. Sadly, Riot doesn't realize that their system doesn't stop leavers, so their methodology is straight up inferior.
If an abandonment happens within the first five minutes of a DotA game, the game becomes safe to leave and no stats are recorded, as well as no BP awarded. Nobody is forced to sit around in an unbalanced game for twenty minutes.
If an abandonment happens after the five minute grace period, the game becomes safe to leave BUT stats are recorded and the normal BP award applies, so there is definitely incentive to finish the game. If you have a leaver/afker on your team you can leave if you so desire but you have to weigh that against the potential win. Leaver/afker in LoL? Incoming 4 to 1 surrender, 100% guaranteed loss.
It goes beyond that as well. DotA 2's hidden karma system suggests that even the leaver/person with disagreeable internet also has reason enough to reconnect and see the game through to its finish.
There's only one question that really needs to be asked here:
Is preserving the facade of a perfect leaverless game really worth the freedom of the individual?
There are going to be leavers in DotA. There are going to be leavers in LoL. Neither system can completely eliminate the problem. So which system would you rather stand behind?
Personally, I feel like DotA 2's system wants you to be more competitive and wants you to earn your wins, rather than trying your hardest to stomp and hope that the opposite team just gives in at the twenty minute mark. But it also tells you hey, this game ended in abandonment way too early, this is not worth the waste of time for anybody.
Does LoL need the safe to leave system? It may be very close to the top of a laundry list of changes LoL needs to become a better game overall.
I cannot understand how there are some LoL'ers that don't want LoL to be like DotA when LoL was born as a DotA-clone. The more Valve continues to do right, the more Riot will copy.
I wouldn't expect to see safe to leave without major overhauls though, the type that demands a ridiculous undertaking, the type that is several months (if not more than a year) long.