Thanks for the comments on my music, I appreciate it. As for the guard gauge: Since the effects are so small per hit it'd be easily noticed over a long combo, much like how most players have a feel for what percent will generate what knockback with which attack.
I can see where you're coming from on forced % damage leading to camping/hit and run tactics, but I think since all "neutral" stages are too small to really camp on anyway, it wouldn't be too big of a deal. If Fox wants to laser camp and weave in and out of your range to deal damage, he's going to do it whether he can kill you with a single laser from forced death or from an upsmash at 150%. It's all a matter of building damage so you can kill sooner or later, no matter the MO.
In better words: the entire purpose of Smash is to build up your opponent's meter so you can kill them. At this level of metagame in Melee, characters rarely ever survive up to 200%. If you can't kill by 200% due to your character's inability to kill one way or another, why not set a cap so they don't have to worry about this? Peach and Young Link will camp and run no matter what, waiting for openings. If the player is good enough to keep you at bay with their projectiles until you die from forced death, chances are they would have outspaced you until they could've blast killed you at 150%
Also, it doesn't necessarily have to be a percent set per character, such that character A will always die at X%. It could be some type of ratio modification: Imagine if we set a base 200% forced death for all characters, and then each individual character has two modifiers: self and else.
For Fox, since he's very light, he'd probably have a high self modifier so he doesn't die at 200%, but instead with a modifier of 1.1 or so his base destroy percent would be 220%. Since Fox is one of the best killers in the game, he would have a high else modifier, probably around 1.3.
Now imagine if he's playing against a Roy. Roy has a very difficult time killing characters since he has no easy setups. If we were to give him an else modifier of 0.8, he'd only have to inflict 176% on Fox.
Peach is midweight, so she's about average for killing off the sides, she would probably have a 1.0 self since she's average knockback. Since she's excellent at killing others, she could probably have a 1.2 else. Peach vs Fox would be Peach needs 264% to kill Fox, Fox needs
As for audio engineering: are you referring to the coding/engineering aspects, audio/music production/composing, or both? I have absolutely no knowledge of audio coding but if anyone knows where to start I can give them all the knowledge needed to make things sound smooth and crisp.
EDIT: this post is all sorts of disorganized. If you can't quite comprehend what I'm trying to get to I'll come back through and reorganize it. I think I even did some of the calculations incorrectly here and there, If you're interested in researching into this concept, grab a pen. paper, a scanner, or type up/blog your ideas.