Yeah but we're past Brawl. It's not better than a meter because first of all, it does not give weaker players a better chance at getting it. It gives them a random chance to get it, the same random chance the better player has of getting it. Also, being an item that randomly spawns, it works in casual play but doesn't spill over into competitive play. We're talking about Sm4sh, which has a For Glory mode that never sees these hype moves. Having a meter would mean it could be used in casual and competitive, and that's what Sm4sh was going for, appealing to both styles.
You can have a meter work any way you want. If it charges faster by getting hit, it's a come back mechanic. If it charges faster by dishing out damage, it's a momentum builder that rewards aggressive play (Did I see something earlier in a thread that said to give players a reason to approach?). Imagine if you could adjust meter gain in the options for casuals and competitives. Randomness hardly ever makes for better balancing, since you seemed concerned about weaker players. Randomness isn't balanced towards the weaker, it's random. And imagine that ball flying around. Would the player who's performing better have better stage control, thus a better chance to get the ball? If you are concerned about the weaker player, make it a comeback METER that builds, not hinged by how far you are back in score as far as stocks, because right now you have to be getting absolutely trounced to spawn with a FS, so it's not even a game changer for the weaker player.
Meters were designed strictly for competitive play. The only meter in the game(s) in general is Little Mac's a very specific gimmick. It is still intended as an overall casual series.
And no, the randomness does not benefit "better" players easier. It's too random for that. It can spawn just about anywhere. Meters really aren't very well-designed by default either, and completely take away from the uniqueness of the game, being items. It makes more sense for the series as an item in both a casual(which the series should still appeal more to casuals since that's the main playerbase) and a "this is how the game series was always designed to be" sense. Meters are not really balanced either, nor do they work well, plus that would not really help the game series feel like its own thing.
There is no real way to make meters work properly and still keep the series designed properly for casuals. It's not really a casual type of playstyle by design either. It also misses the point of why they're items; A way to uniquely control using that overpowered move. The best balance, while keeping it random enough(which makes the game series work better in the long run), is to balance out the Final Smashes more. Also, the idea of Final Smashes being item-only also is intended to be created solely for casual play. Competitive play is not about some overpowered move in general. It's about using your character with the specific rules(generally no items, and balanced courses) to beat the other player using purely your own skill. The fact Final Smashes were designed as basically special items to use is relevant to the series. It's always been an item-based series. It'd be a pointless change for the sake of it. It doesn't make the game more unique either, but just tries to make it look like tons of other competitive fighting games. Smash 4 is still designed to appeal to casuals, and it does a great job at it in general. It removes a good chunk of the randomness, but doesn't eliminate it entirely, still keeping the series' fun design intact. Since Brawl, they've taken away the extremely specific controls akin to regular Fighting Games(bar Ryu's own gimmick), meaning a lot of the Input Commands are gone, a feature that is intended to be for
competitive fighting games. Some of the most notable Input Commands were Wavedashing(gone), the original Dancing Blade and Roy's clone version of it(both were made far easier to actually use, although getting which one you want is slightly more difficult, but it's harder to screw up the overall move in return). This made the game series far more accessible.
Meters really don't appeal to a lot of gamers because instead of just having fun and going for that neat item(a huge thing that is part of the game's main design, when items are on), you just concentrate on tanking, which would apply for all characters. It's too hard to balance around tons of super unique playstyles, lack of a Hit Points meter(the HP meter actually does make Meter gameplay more accessible because you have to be even more careful when avoiding to get hit), and only benefits characters who are too powerful or can tank hits better than others. They're not really designed around a percentage system. Rage already covers the idea of increasing your stats if you are too high in damage/take hits too often. This is fine because it actually works well for this kind of series. It's designed directly for Smash. Meters works fine for someone like Little Mac, but it'd require a huge revamping and way too much balancing when the Smash Ball already does the job well while appealing to the players that actually use items. The only way for it to be fair in competitive play is if the Final Smashes were not very powerful at all, and also had to be reduced to an extremely specific amount per match, which already starts to sound far more boring than the official version the series uses, which actually is more fun for all kinds of players.
's Final Smash ought to be something that fits her archetype (and yes, I made only female Miis). Make the Brawler's Final Smash a transformation-type like 
