I think this is one of those examples of trying too much for little gain. At most, Phil might get salty and complain about detractors, but you could easily achieve that same end result just by going into his chat and making one or two generic troll comments. It also feeds into his victim narrative, since he can point to it as an example of the detractors ruining his livelihood, and since it is likely to fail it'll also puff up Phil's ego when nothing ultimately comes of it and he can act like it was some big victory on his part.
Even from a detractor standpoint, I think it's better to let him carry on with his merch. It seems to net him barely any money so it doesn't actually help him, but we usually get a laugh about the badly designed shirts. Something like this also just seems like more effort than Phil is worth. I think part of what makes Phil such a popular cow is how he's his own biggest detractor. You don't need to start a twitter campaign against him, and honestly, any twitter campaign against him is likely less effective then the own twitter drama he starts by calling other people shills whenever there's a new release.