Hi guys, I've been inactive lately, but I've still been in the lab, and I might have some new proposals by the time I get back, but in the meantime...
Neutral Get-up to Bowser bomb wins pretty reliably for me, it's best to bait the opponent into trying to hit you then timing the get-up so they just whiff through your I-frames. If you time it well, there are a good number of things which can be punished with get-up to various options. Just think of it like a spot-dodge.
Also, Air-dodge cancel specials from the ledge might be worth trying if you haven't already, they work pretty well, and you can even do b-reverse down b to jump back onto the ledge to refresh your ledge I-frames if you want. I think a good use for them would be against players that like to punish you early for ledge hopping with a grab or dash attack, since you could probably fortress punish most of those in time, and even move to the center stage to make them launch offstage. Edit: I should note that Non-Omega Battlefield and Lylat gave me a lot of trouble when I was testing it on those stages. The easiest stages were Delfino and Halberd, in fact on Halberd it's almost too Easy. On Lylat it's doable as long as you mind the tilting and ledge slopes, and on Battlefield, it's just incredibly hard because of the shape of the lips, you have to neutral jump then drift and it can be very tricky. Every other stage, especially wall stages, weren't too bad.
On another note, not sure how useful this is exactly, but while I was doing some research, I noticed that grass counts as higher traction terrain. This affects a few various things, but perhaps most obviously is that grounded movement is slightly, though noticeably, better on grass than on other surfaces. If you want to test this then go to Omega Great Cave, and do a run-stop dash dance on the purple side of the stage as fast as possible, then try it on the grassy side. You should notice that you will be able to initiate each dash with a smaller gap in between them. You'll also move forward less distance during a run before your shield can come out, meaning running is potentially slightly safer on grassy stages. This might be helpful in matches versus projectile-heavy characters. I apologize if this was already known information.
There are five legal stages with Grass, all of them are Omega stages, (Mushroom Kingdom U, Galaxy, Yoshi's Story, Great Cave Offensive, Windy Hill Zone) I imagine some characters, like Luigi, would technically become slightly better on these stages because of the increased traction. It might not matter much in the long run, but I guess it's something to consider.
Hope that helps!