You also need to convince the guy to make a dictatorship, making it harder, he'll be non-partisan, it would allow more checks in power, plus this monarchy system is an Unionese system. The Monarch would have to be elected, and would rule for life. When the monarch's reign is over, his family proposes a candidate, along with other people. Depending on the result, the ruling dynasty or another could win. The Monarch cannot have any connections to the financial system(as in, being a bank executive or employee, be a stock investor, receiving donations, etc.), along with his family. If any royal wishes to have connections to the system, they would have to resign to their royal position and to all its benefits.

Plus, who doesn't like decor?