Honestly, I saw it, but I think it's not a problem. A foot can strech like this during a run.
The bigger issue there is that this means the run animation is uneven. And not just that it's uneven, but that it's uneven in a really weird way.
On the subject of GSS feedback overall: It's an awesome PSA. That movement speed glitch when firing a Super Scope/firing a Ray Gun/holding a Cracker Launcher ought to be fixed, however.
DThrow > short hop > DAir > DSmash > NB is a really good combo, as you mentioned. It also works with FSmash instead of DSmash > NB, and in fact does more damage that way. But FSmash is a really good kill move when using pistols, so I tend to want to keep it fresh.
Dash Attack > SideB + extension > UpB + extension is a nice, fairly safe damage-building chain. She moves a lot during it, which makes it hard for the foe to pin her down, and she has intangibility at two different points in the chain, along with a really low stance during the dash attack. I say "chain" because it's not a true combo, of course.
Her crawl seems really good. I know it's just the same as ZSS's crawl, but somehow it works wonders for GSS's playstyle. Just being able to shrink your hurtbox way down helps GSS sneak through projectile camping tactics that can really irritate her. And then when you get close enough, either use Up Special or go for SideB into Dash Attack, then the attack string listed in the above paragraph.
Aerial SideB's extension would really appreciate the ability to reverse it after the confirmation hit. It's an idea that was brought up earlier in the thread, and one I think would help that move considerably. Especially since it's easiest to land when pursuing a foe who's already been hit or who is running away, but will frequently send you to a Self-Destruct if you actually do so. Being able to reverse it, so she can flip back to the stage instead of out and away from it, would help that problem immensely.
Forward Aerial with pistols still doesn't chain its multiple hits very well, and the final hit still has nowhere near enough KB considering the current difficulty of landing it. It doesn't help that the attack takes long enough that it can't be executed with a short hop. I'd say the final hit ought to be on par with her Back Aerial in terms of KB, and/or it ought to link better overall. Whether that be through knockback adjustments or simply speeding up the move so it can be executed from a short hop doesn't matter, as either will work. It's definitely a very situational attack as is, and in most situations where you can use it there's a better option available.
Down Aerial with machine guns really doesn't need the hitbox extending all the way to the tips of her feet, if you ask me. In fact, her body shouldn't have hitboxes on it at all during that move. Just on the guns and over their range to the distance it currently reaches.
On another note, many of her attacks with the machine gun behave oddly with time manipulation events. In particular, GSS's FTilt + Deadpool's DownB = Deadpool taking twice the damage he should instead of countering. I'm guessing that's due to rehit rate.
And on the subject of her attacks' range, an interesting real-life tidbit: I read somewhere that a Hollywood-style blank can still injure out to a range of two metres.