Well, making a single tree for all "other" nations would be, imho, not a good idea (literal flood of vehicles and designs). So, why not just make shared trees, where it follows some kind of common-sense - in terms of tech used, mindset, or political setup of the world at that time?
In this post, I would like to focus on gathering as much info on Swedish tech (vehicle types + rough performance) to support the idea of including Swedish tech in the main tree of Britain and later making a proper suggestoin.
The countries were on very friendly terms before the WW2, a lot of tech after WW2 comes from Britain either way (some pre-WW2 machines too) - and Sweden are on friendly terms with NATO up to this day.
So, to start this up, I will list a few common vehicles that support this idea:
Gloster Gladiator, already in the game.
Strv 81 (Centurion mk.5)
Strv 101 (Centurion mk.10)
Strv 102 (Centurion mk.10 modification)
Personaly, I think Swedish tech would only enrichen the British tree, while keeping the default mindset unchanged. This is also supported by the fact that there is already one Swedish tank on the British tree, even if as a premium.
I am going to edit this post, making slowly a list of potential vehicles, again, this thread is not a suggestion, this thread is to make a list of vehicles that could be used for a tree - that can be put into a suggestion.
And here a motivational Strv 102 in swedish camo to end it off.