A Nordic federation's bases and sea-control problem

Which naval bases would suit a hypothetical Nordic federation formed in 1919?

The federation would possess strategic depth and resources but also an enormous defensive perimeter, requiring Baltic sea control, Atlantic infrastructure, destroyers, and a close relationship with Britain.

The proposed federation joins Sweden, Norway, Finland, and Denmark, with Stockholm as its capital and purchased Orion-class battleships and Lion-class battlecruisers. Trondheim and Reykjavik are suggested as major Atlantic and North Sea bases, with Narvik and the Faroe Islands supporting destroyers and submarines. Denmark's responsibility for Icelandic foreign affairs and defense under the 1918 union makes Iceland's inclusion plausible in this scenario, alongside Greenland. The federation would combine substantial resources and strategic depth with a limited population and a wide defensive perimeter. Baltic sea control would be necessary to carry reinforcements to exposed Finland and Denmark. Protecting Atlantic fisheries and possessions would require further bases, infrastructure, and many destroyers. A close British friendship is considered likely, although a formal alliance is not assumed.