Take away all their other tools, he'll be fine with it.
Some real talk for a second, but I find that this in particular is what bugs me about a handful of the "good" melee characters. People like to chastise that PM characters are full of gimmicks and whatnot, but to me a gimmick is something that a character essentially relies on in order to function,
or is there for highly situational usage. Sheik for example had her dthrow in NTSC melee which is an example of the former (though she did not really "need" it, it dominated her play for a while) and an example of the latter with her ability to transform into Zelda which in melee acted as a situational recovery option and in PM can actually be a sort of mix-up given that Zelda is a legitimate choice in some match ups.
Taking away the Dthrow gimmick and buffing Zelda essentially ironed out her gimmicks, and yet she is still amazing in PM. Sheik doesn't really have a real gimmick in PM in that there is no one move that she really relies on to function, hell you can use her without needles and still do work thanks to her other tools. Now, take away Fox/Falco's shine and suddenly what happens to them? Their shield pressure goes away, their combos (especially Falco) become much lesser, and even situational uses such as momentum stall and actually reflecting stuff (especially Falco again since his is lagless on reflect), essentially their power goes right out the window even if they kept the lasers and Uairs/Usmash/Dairs/etc. Other examples would include Rest/Bair (though that is talked about a lot already), and even things like PK Fire. Those two examples are from bad/mid characters but that doesn't exclude them.
While the shine example is a bit extreme/exaggerated, my point still stands that if taking away a single move can essentially destroy a character's potential overall then it is gimmicky. Many "top" characters have moves such as these but at the same time do not have other weaknesses like Ness and Jiggs do that counterbalance the gimmick of that one move (or two). Melee characters with these sorts of things have resistance to change due to sheer time that the tools have been around and all the play developed around them, so it's only natural that alterations would be met with healthy skepticism if not outright anger. But at the same time, other characters had similar "radical" changes and people have been maining them for 6-7 years as well, yet are nowhere near as vocal (just think about Brawl Lucario mains for a sec... I don't think anyone else got as radical an overhaul). People are fine with changes like that, but it seems when the gimmicky bits that let people dominate in the past come into question is when people really take up arms.
In conclusion here, nobody should be safe from change as a TOP melee vet has already seen significant change in the form of a viable down B and non gimmicky dthrow, and another TOP is crying out for change in order to be relevant again. Both of those seem to be accepted by the community while other aspects aren't. If this game is really about balance, we should not allow character bias to dictate game play as that just drives a wedge between the community in various ways and that is more toxic than any buff or nerf you could ever code.