I’m almost wondering if we should just have a federal parliament with an upper house of individual state-appointed voting ambassadors, and a head of state that is rotated between governors every 2 years.
It may be wiser to have to “president”(head of state) simply employed by the leglsator, so that he maybe kept subservient to the sames lawmaking power?
I of course like your idea just as much, I do however think some states may need their govenrers full attention for their own government.
My other thought on the matter is that the justice system of a new union should be strictly limited to deciding jurisdiction(before trial) rather than cases.
In cases of clearly international nature perhaps a rotation system as you suggested might be in order there as well? Likewise in cases of dispute between States a 3rd party state seems most logical?