I believe both Sedunn and the Frost Empire (and technically Karnetvor) would have high-ranking personnel with even more experience (from joint campaigns in Reizen, Transsuneria and Tasternine for instance, and a strong tradition from the Great War), but Sedunn of course wouldn't have a problem with a Stoinian becoming secretary general, especially since Sedunn wants to avoid giving the CE an image of a Sedunn-run organisation. A secretary general however, isn't normally someone who commands forces, but rather someone that oversees political matters. A Sedunner could maybe be first chief of staff or similar for the joint command that shall be established too?

Sedunn would accept Reizen as HQ, provided that the Empire adheres to international law in its special military operation, and especially respects any decision by the legitimate government of Spiras.

There's very likely an embryo to a joint CE joint staff, noting that Sedunn, Stoinia and the Empire ought to have coordinated their operations against the nationalists in Spiras and on the seas. At least in order to not shoot at each other and so on. Sedunn's current involvement is primarily a response to the nationalist rebel naval campaigns, destroying equipment, infrastructure and other important targets that could support further aggression towards Sedunn and the international shipping lanes. Sedunn would seek a WF mandate rather than a full CE intervention at this time.

Regarding nukes, Sedunn would not support a policy demanding ratification of the TPNW before joining the CE, as it trusts the organisation's ability in letting only responsible nations join.

In conclusion for the most pressing matters: it's an Aye from Sedunn and Transsuneria on the main HQ in Reizen (with the condition mentioned above), and General Corina Noica as secretary-general.