Player Tribunal was dropped essentially because players abused the system and trolled.
That was only part of the problem, and it was abused because there was a reward incentive tied to unanimous case votes. The other problem that the Tribunal had was that it was very slow to get punishments out, and wound up with a backlog of reports to file through - as well as players getting punished for misbehavior from months ago.
Bring the Tribunal back, but only players who are honor level 5 can review cases.
This...Is already not a great idea. The Honor Level climb is supposed to be a year-long thing, and IIRC, even people who play frequently would take around 7~ months to get to Honor Level 5. If Honor Level 5 was a prerequisite to Tribunal participation, then the Tribunal would only really be active for around 5~ months; from August 'til January, when Honor Level resets.
That leaves a whole lot of time for the Tribunal to be completely unused, and ironically, would lead to the issue of having a backlog of reports and punishments being dealt way, way, way later than they should've been.
The case is given to 3 players, and majority ruling determines that player's fate. If a player is in constant minority when judging (aka they're trolling), then they will no longer be asked to review cases.
Three reviewers doesn't really sound all that fair, to be honest. With only four possible outcomes (3/0, 2/1, 1/2, 0/3), you may as well call punishments a coin-toss. And the last thing you want with a system is for punishments to basically boil down to a coin-toss. You need a larger pool of reviewers if you're going to punish players based off a majority vote.
And that brings up an issue; speed vs. accuracy. More reviewers means that a verdict will likely be more accurate (there will be less likelihood that the punishment just swings to one side, as it would with three reviewers), but it would take longer as there would be more people needing to review the behavior. On the other hand, less reviewers means that verdicts can come out quicker, but it also results in less accuracy because the punishments are being decided by all of three people voting "yes" or "no".
Additionally, punishing reviewers for being in the consistent minority has some issues, especially when coupled with the low per-case number of reviewers; outside of unanimous votes, someone is going to be in the minority in a case; how many times is that going to happen before they get penalized? And how does their being in the minority somehow determine that they're trolling? If a punishment only needs two votes to pass, then the minority vote shouldn't eventually be omitted from the system - 'cause, as mentioned earlier, there are really only four outcomes.
You can't determine trolling just by someone being in the consistent minority; you can't tell if they're deliberately voting differently "for the lols" or if they're actually seeing something that other people aren't. Attempting to determine trolling/misbehavior solely by someone coming up in the minority vote frequently would just be arbitrary. That'd be like judging trolls by KDA alone; every non-kill-focused Support would become a troll by that logic.
Players who review cases can get a minor reward, like maybe 100 orange essence: nothing too big, but enough to give incentive to review cases.
I would not call Orange Essence a minor reward. Blue Essence, yes, but Orange Essence - which can be used to unlock all sorts of cosmetic Shards for free? No.
And, again, this brings up the issue mentioned earlier; people tended to troll and abuse the Tribunal when there was a reward attached to it. And if people just spam-voted "punish" when rewarded with Influence Points (Blue Essence) for successfully passing a judgement, how bad do you think it'd get if they were rewarded with something more valuable (Orange Essence) just for participating?
...as those who r lvl 5 honor are more well behaved then the majority of players...
I'd say this assessment is a bit too idealistic of the Honor System. Like Champion Mastery, Honor Level doesn't actually equate to what it's supposed to represent all that accurately. Just as Champion Mastery is more literally a player's time playing that Champion and their ability to get a couple S ranks as them, Honor Level is more indicative of a player's ability to play League without getting punished or validating reports.
I just think it sucks when a player is unrightfully punished because the bot detected something that was taken out of context...
I would like to see an example or two of this, because by and large, the IFS is pretty damn accurate about judging chat behavior.