The protector, the two secretaries, the council of state, with any five or more that the senate appoints, are possessed, on extraordinary emergencies, of dictatorial power for six months.--Hume, Idea Of a Perfect Commonwealth
In Hume's plan for a perfect commonwealth (recall this post), foreign policy is insulated from democratic control. He lodges it in the "council of state" which includes only three members: "The protector and two secretaries have session." These three members are chosen by the senate, which has some kind of function in deliberating about foreign policy. (Hume is not entirely clear on this point.) It turns out that the the three members of the council of state are the core membership (of eight) of a dictatorial junta in "extraordinary emergencies." That the council of state is always part of the dictatorial junta suggests that for Hume the emergencies arise, if they do, in foreign affairs, especially the context of war and conquest.
As an aside, Hume's willingness to plan for exceptional circumstances with the abrogation of the rule of law in "what is the most perfect of all" possible political orders, is noteworthy because (a) Hume tends to be associated with a firm commitment to the rule of law and (b) with a kind of conservative commitment to the value of tradition. While Hume does not go so far as Walter Benjamin [recall] in treating the state of exception as the rule, he recognizes that it must be planned for.
In one sense, Hume's proposal is a nod to Livy's famous account of the dictatorship of Cincinnatus in Republican Rome. But Hume is explicit that his commonwealth is an improvement of ancient republics because he thinks these as "oppressive." Moreover, he has little fondness for Ancient Republicanism (which requires slavery). So, it would be a bit odd if he is really trying to make space for a modern Cincinnatus.
A better sense to understand Hume's treatment is to take him at his word, and note, first the "resemblance that [the blueprint of a perfect commonwealth] bears to the commonwealth of the United Provinces,a wise and renowned government." One of his improvements over the constitution of the Dutch Republic is by his own light the removal of the veto power "which every province and town has upon the whole body of the DUTCH republic, with regard to alliances, peace and war, and the imposition of taxes, is here removed." So, Hume's perfect commonwealth is not a confederation, but a federation that can act as a true unity in foreign affairs and even in an emergency.
In fact, Hume has also modeled the dictatorial power on a particular episode in the history of the Dutch Republic that he recounts in the History:
But the greatest difficulty still remained. By the constitution of the [Dutch] republic, all the towns in all the provinces must give their consent to every alliance; and besides that this formality could not be dispatched in less than two months, it was justly to be dreaded, that the influence of France would obstruct the passing of the treaty in some of the smaller cities....To obviate this difficulty, de Wit had the courage, for the public good, to break through the laws in so fundamental an article; and by his authority, he prevailed with the States General at once to sign and ratify the league: Though they acknowledged that, if that measure should displease their constituents, they risqued their heads by this irregularity. After sealing, all parties embraced with great cordiality.--Hume's History of England
I have already noted that Hume has, despite his fundamental criticism, very high praise for De Witt. In the quoted passage, Hume praises De Witt's courage and public spirit in risking the charge of treason by breaking the law (that gives all the provinces a veto power over treaties) in the case of an emergency (in foreign policy). So, Hume designs his own ideal state to make space for future leaders that can make public spirited decisions without too much constraint. But rather than trusting a single person with emergency powers, he assigns such authority to a small group; in addition, he requires the senate's judgment that there is, indeed, a state of emergency. It is an open question if Hume's approach does not lead to the oppression he dreads.