"Harmful paraphillas" and "the big three" have always kinda bothered me as terms, as they sort of beat around the bush about the actual problems and what is being talked about, so here's an alternative I thought of:
Impossible-Consent Paraphilias.
This makes it clear what's actually being referred to (paraphilias that cannot be consented to) and without the implication "harmful" has sometimes where anyone who has them is inherently going to cause harm. It allows for expansion in the way "the big three" does not, and is also more clear on what it actually means without context on what "the big three" actually are.
It also avoids including ageplay, petplay, or consensual non-consent, as these are all things which can be consented to (though obviously your mileage may vary on your interpretation of them otherwise).
Not sure if this'll catch on or anything, but if anyone else was uncomfortable with the common phrasing, I wanted to share my alternative.