I personally think that Sweden has been lacking in top tier planes and could use a sub tree, specifically Norway, if they did add a Norway subtree it would get the F-16 for top tier and F-35 for a future update.
With the finish f-18 being added it was a disappointment no hmd and no air to ground Gripen is the only good top tier plane they currently have (imo)
Norway subtree could include things like F-16 Fighting Falcon, North American F-86K, Republic F-84G, F-104 Star fighter, Northrop F-5
(Found this at Royal Norwegian Air Force - Wikipedia)
Or Denmark.
Denmark also uses the F-16. Denmark could get the Gloster meteor, F-84 thunderjet/thunderstreak, F-100 Super Sabre, Saab 35 draken and the F-16 fighting falcon
Both of these subtrees are great options but in my opinion i would say norway because we already have a draken in the tech tree and norway already has the event F-5a
If u have any ideas please say them