Playstyles matter very, very little if you are restricted within your moveset.
No matter how you use a move, if it is punishable. You should be getting punished for it.
Le gasp.
Consider the following.
A Meta Knight uses Forward Smash and somehow (we don't care how) progresses far enough in the execution of the move for the hitboxes to come out. Meta Knight is in range to hit the opponent or his shield. Now consider two different ways he could have been using Forward Smash.
Way 1: Meta Knight was facing toward his opponent.
Way 2: Meta Knight was facing away from his opponent.
By the suggestion of your post, the punish-ability of these two should be equal. Anyone with common sense and a decent knowledge of Meta Knight will tell you that Way 1 is mostly unpunishable (powershield only for punishing) while Way 2 is punishable in general.
Brawl as a fighter has something called "depth". This means many things; one of them is that the optimal way to play is non-obvious. If it were obvious, several players would employ it, and results from play among these players would be essentially random (since they would be playing the same). We know, therefore, that everyone is employing some sub-optimal strategy, and furthermore we can observe easily that everyone employs a different sub-optimal strategy. A player's particular sub-optimal strategy is what we might call a "playstyle". Obviously, in tournament play, you hope your particular sub-optimal strategy is less sub-optimal than everyone else's (if it is, you will probably win the tournament). With the Meta Knight example, we might consider two players who use Forward Smash in those different ways. Player A uses Way 1 while Player B uses Way 2. When Player A uses Forward Smash, it is not punishable. When Player B uses Forward Smash, it is punishable. We might even consider the opponent not being optimal at punishment; maybe some opponents will fail to punish Player B.
Of course, particularly sub-optimal elements of your overall playstyle, such as Way 2 in the example, are likely to be rooted out as you improve. However, your playstyle will ALWAYS be sub-optimal. You may always be mediocre at spacing move X (not necessarily horrible, just mediocre), but it's okay since you're really smart about when to use risky but very rewarding move Y, better than most players. In any case, of the game elements you have at your disposal at any given time, you are likely to favor which ones you utilize more heavily based on your personal strengths. If you are really good at spacing move Z, you will use move Z more than some mythical optimal strategy probably would... and be rewarded for it. If you just really can't get move X down to the same level of usefulness as other people who find themselves in the same situations, you probably won't use move X as much as other players. You are also going to have subtly incorrect valuations anyway. Maybe you believe move Z to be slightly better than it really is while you believe move X to be slightly worse than it really is. It all adds up, and it is why playstyle has a huge impact on the progression of matches in every way, including the safety of moves. Of course, you could stick to your original and completely absurd suggestion that moves have some arbitrary "safe" versus "not safe" property, presumably hardcoded via a flag the hackers somehow missed, and that safety is definitely not dictated by timing and spacing in a variety of subtle ways and further influenced by matchup and stage and the allocation of various resources such as lingering objects like Snake's grenades or staleness or shield health such that even if one high level player gets punished in a case or two for a move it may not be generally punishable. It is definitely not highly likely to be situationally punishable, that is punishable only depending on context.
I don't know what you're trying to get at, but you are defying the rawest of basics of fighting games in a truly absurd way. I really hope you are just poorly expressing what you mean.
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