Right, I understand what you're trying to say and I do agree with you. However, you cannot just opt for a remake opinion half way into a match. The last paragraph describes exactly why you cannot have a 'remake' option through out the entirety of the match.
And, no, I won't sit here telling you that you can majority of 4v5 matchups as it is just way too much pressure. If you lose a support no big deal, right? Unless that support is 75% of your hard CC. Such as a team revolving around a first pick Leona. Or if you lose your jungle, unless your top, mid, and adc are able to maintain proper lane pressure. But, that is all subjective and requires an ungodly amount of teamwork.
Now, my other suggestion would be a in game buff. Depending on who lefts the stats get split up among the team. If, for example, a mid Brand g disconnected, and the jungle has to jump back and forth between mid and jungle, then the stats of brand, per level, should be shared among the team. So, if the jungle in the example is, nocturne, then he gains extra health, armor, attack speed, etc. this in turn goes for the rest of team. All the way up to, either Brand returning, or level 18. This in turn could help even match ups against a 2v1 bot lane. Even if the ADC disconnects, at least the support will have enough in stats to stall the lane to deadlock. This in turn makes it harder to bulldoze a lane and gives enough pressure for a psuedo 5th man.
This, is what I think should happened rather than a remake opinion through out the entirety of the match.