The issue is that there’s no way to have a fifth move just in reserve for that situation, so it would make T-Spikes and Icy Wind a 2/3 roll with the added move. I think the niche L with that is better than making Qwil-H worse 2/3 of the time because it doesn’t have one of its best support moves.
imo it wouldnt make qwilfish that much worse - tspikes are good, but a set of taunt/crunch/gunk/icy or taunt/tchop/gunk/tspikes are both perfectly valid and decent sets. moves like taunt that could replace them just arent as bad as youre making them out to be.
if you really dont want to lose icy or tspikes, then why not just get rid of crunch or throat chop from its movepool, and have 2 users of tspikes. the slight benefit in surprise factor from throat chop or crunch is worth very little to begin with, and most tspike setters rarely want to/are able to get 2 layers of tspikes up, qwilfish especially given how useful intim is.