I just started playing around with Z-PS after reading about this myself, but it made me think back to a thread I read a few days ago about hand positioning on your controller, namely this one:
(taken from here
https://docs.google.com/document/d/1ANO0i36RvUm9DI3kXI4SkyyE2nnG4PLdPd0KS4S3KL4/edit)
So I'd be holding the controller similarly to him in that picture, with the minor difference, that I'd be pushing down my thumb further, making it rest on the a button, keeping it activated. From that position, I was able to do any moves fine with just 5min of practice. Your thumb naturally touches y's edge without moving, so you can input jumps/wavedashes without letting go of a and if you want to attack, you do the normal movement as before, as if you never pressed/held a. My rising aerials didn't feel slower, could still pull off my double fairs to the left and right consistently with the c-stick. Dunno if it impacts rising aerials with a, as I don't use a for them, except for the obvious nair, but I guess with a little practice it should also work.
My conclusion so far is, that it doesn't impact your movement nor attacks (Marth techskill), downsides to be found..
But remember, that's just my first impression from playing around with it for a bit, no idea how comfortable it would be to play like that for a full set. I consider it an option select* atm, since I don't see a downside, yet, where you simply hold a after every single wavedash, unless you want to attack obv, and using wavedashes is pretty common in Marths movement, so you should be ready to Z-PS at almost any point in time.
What does bother me is, that you need to press L and Z at the same time for it to work. Is that true and how tight is that frame window? Is it really the exact same frame? And does that refer to the full L press, all the way in, being timed on the exact same frame as my Z press?
"Thus, the necessary inputs for Z-PS are:
1. Keeping A pressed (can be done during wavedash lag, during the frames 1-3 of a dash that was not done out of turn if the stick is not held forward and during
RunBrake , and these are just a few examples)
2. Pressing DP and Z at the same frame"
(from Kadano's post)
Another setup I found in Kadano's post that is actually better than wavedashing and will maybe? work well with your dash back method:
"Setups
Dash: during a dash that is
not done from a dashdance, you can hold A during the first 4 frames (while having the control stick at a neutral position. This was found by
@schmooblidon and is the fastest A buffer for Z-PS."
Thus wavedashing (an obvious setup) isn't even necessary. Or maybe even hold a during the stage loading screen and just charge Falco and if he dares to laser you're ready to PS chaingrab to death lol. Poor Falco if this is actually easy to master.
I'm pretty curious if you already came up with something as well, this looks pretty promising to me, except for the same frame part, don't know how hard that is to be consistent at until I try it more tomorrow. Also, sorry if this post is kinda messy, I'm very tired..