A full parliamentary system is what we essentially had under previous constitutions and it largely worked fine but didn't give the delegate enough quick acting authority in defending the region in the event of an invasion.
Given the mechanics of the NS world, a full parliamentary system in which the Delegate is essentially a Constitutional Monarch and everything else is done by the legislature and Prime Minister is more practical. But, I like the idea of the Delegate having ultimate executive authority under the Constitution - and if the Delegate chooses to delegate that authority to others (like appointing a prime minister or having one elected from the RA) it would take some of the load off the Delegate.
Such a system would tend to create an environment where the Delegate is 'above politics'.
The disadvantage is that in the event of serious defense problems, the Delegate may end up restricted and delayed in that department without full executive authority.
Addendum:
Personally, were I Delegate, I would prefer to have someone like a prime ministers to handle the legislative issues and the day to day mundane government functions, and then rely upon the Cabinet acting in the capacity of 'advise and consent' on decisions that are solely the function of the Delegate.
This would imply a system in which the Delegate would rely upon the advise of the Cabinet in matters which involve checks and balances and other constitutional duties. This would leave the Delegate with chief executive authority with the concentration being on executing the Constitution and Laws as required of the Delegate.
This would somewhat give an element of a bicameral system with an additional element of checks and balances if the Cabinet is given over-ride authority like the RA. The question here is do you go back to an elected Cabinet or an appointed cabinet?