Firstly, Brawl- is a mess, so citing it is like saying glue is edible because preschoolers have done it.
Second, that's not the grappler archetype. The grappler archetype relies on poking, short combos, and out smarting your opponent and landing your punishes based on that. This only works when your mobility is greatly limited, a la street fighter format. Think Zangief.
Edit: I know they say they have stuff inspired from Gief, like the running bear grab, but it just doesn't serve the same purpose as it does in street fighter. The point I'm making is you could make Bowser into something like that, but it's fundamentally not a grappler, and wouldn't fit in the P:M environment based on the mobility offered to the rest of the cast.
What version of Brawl- are you looking at? 3.3 is great, 3.5 is hardly a mess (Samus...), and 3.Q may have an odd changelog because some of the devs apparently lost it and started changing something things [seemingly] willy-nilly, but Bowser wasn't affected by this beyond having to deal with a few oddly buffed characters.
Bowser relies somewhat on his Royal Rampage (it isn't called the running bear grab anymore) and his combos are short and devastating indeed (unless you use the right throws, that set your opponent up for more throws - at which point they're moderate length and disgusting). Also you have to outsmart with both the RR (or else free punishes all day) and some other moves (his fsmash is fantastic but high risk of eating a ton of damage before one actually dodge-cancels it (or eating damage because of dodge cancel)). He usually gets a KO off of two successful RRs if done properly, because it is RR dthrow -> Flying Slam -> X, where X is pretty much anything (the Flying Slam grounds people and the RR ground-bounces them, and I'm pretty sure it can't be teched either).
He's also got decent enough pokes in the form of his ftilt and jab. I'm not saying it's perfect or anything, but it's not as bad as you're making it out to be.
And you can b-reverse his Royal Rampage/Galactic Crusher (that would be the aerial super-armor grab) [yay Brawl engine], and you can also opt for the somewhat faster and still very rewarding (But less/no armor, not sure at this point since I don't play Bowser in any iteration of this game) Flying Slam.
GeZ said:
Smash is totally mobility centric. Have you noticed that those "more popular characters" place better? And they're uniformly highly mobile. That's the nature of the game. Same way that Bowser and Ganon haven't been good in most of the games they've been in, and even in P:M suffer because of their poor mobility. I like the cast diversity, and I'm not suggesting a normalization for Bowser/ Ganon/ big characters general, but as it stands now they need something to counter act the inherent disadvantage they have from being less mobile by nature.
Also, while some of those qualities resemble the qualities of a grappler, they don't mean that Bowser fits the same template, or comes close. Smash just doesn't allow for grapplers. The uniform mobility for the whole cast ensures that.
For the record, I don't really think Bowser should become a grappler archetype either, but it is possible if you make certain traits of Bowser polarizing/extreme enough. I don't know if there would be/can exist a happy medium between "This character sucks" and "this character invalidates the cast besides ICs who have port priority" though. Since people were suggesting it, I just decided to throw out the mod as an example.
If you still disagree, whatever - again, I'm not pushing him as a grappler, just explaining how he works in a game you seem somewhat out of date on.
EDIT:
GeZ said:
That's just not true. Any of the perfectly well balanced characters in the game would wreck a grappler as well. While strong characters don't help their chances, they don't exist even in a relatively fine environment.
Think about it in a sense of this, your opponent jumps at you. You predict an attack from the front so you use an armored grab. They can WL/ hit you from behind/ beat your grab with a move with better priority/ stuff it with a projectile.
The only way to counter act that is to make the grab reach in every direction and have full priority against all other moves, which is bad balance in and of itself. Spot dodging alone makes it so there can't be grapplers in smash. Functionally the game provides too much of an uphill battle as grapplers rely on characters having to commit to decisions, like jump arcs, or dash's.
Bower's RR beats spotdodges that aren't frame-perfect (and some can't really spotdodge it at all), and Brawl- has spotdodges much closer to vBrawl length - since PM adjusted spotdodges to be less safe (or so I've heard), Bowser's RR actually wouldn't be spotdodgable, which sort of moots out the spotdodging argument. (You can definitely roll out of the way though). Also, if you think they will attack you, wavedash back RR would answer this - if they've committed like a Captain Falcon jump, they won't have the space to land behind you, and tromping forward will cover landing in front - and there are literally no moves that beat the RR in Brawl- (like, I Warlock Punched him, so Bowser was operating at 700%, but he still grabbed me out of it). The projectile is the only respectable answer, and that would only be if you expected them to attack way more than they actually committed to.
Then again, grabs that can't be spotdodged don't really fit in PM because dev's visions (spotdodging is a mechanic to beat and punish frequent grabbers or something like that) so it still wouldn't work....