Genuine question: does this require IP though? What prevents the subsidiary from paying the parent for "consultancy" or any other amorphous but non-IP service instead?
Most activities can be quantified, at worst by looking at sector averages. There is already plenty of tax law around those, about what you can and cannot realistically expect tax authorities to believe. The IP field, though, has massive value swings, that make it fundamentally uncontrollable. How much is the word "Starbucks" worth? How much is "Nespresso" or "Linizio"...? These can move hundreds of millions in one go, whereas you would struggle to achieve it with murky consultancy contracts over several years.