Agreed, the UAE is an excellent place for tax residence.
Since he wants to live in the EU for at least six months a year, he just needs to be careful not to trigger tax residency outside of the UAE.
To my taste, UAE, with its 45+ degrees in August, is a tad too much, and likewise, winter in Europe is not that enjoyable climate-wise. I can imagine many︀ people would feel travelling around would be the best solution.
You will be fine if︁ you can afford to travel around maintaining a semi-habitual abode in certain jurisdictions. I can︂ imagine that it can be an acceptable balance. Stick to Cyprus, Malta, and maybe some︃ Eastern European countries or countries that are not super aggressive in taxing you, and you'll︄ be fine.
Not everyone wants to live as a nomad their whole life. For example,︅ if you need to school your kids, this lifestyle becomes more complex, so potentially, some︆ sacrifices need to be made.