So... you not only can't kill the player, but for some reason you're RIGHT in that uncanny valley where you can't get a large % lead but also can't kill them... I hope you realize how silly this sounds.
If you can get and keep a 50% lead against a char who is ridiculously good at wracking damage and killing, kudos, you deserved to win.
Well, here's the big one. In normal brawl, without rules, the game ignores % leads. If time runs out, your % lead does not matter. You need to have a stock lead in order to win and not to draw. This rule is a fairly simple compromise, although I still prefer not going by % lead.
Which is why you plan every tournament as if every match would go to time. And yeah, people will be struggling to time out for that rematch. So?
I don't really see tournaments lasting that much longer because of this.