Mikoyan brought up a good point and I think I'll do my best to explain what I'm going to do about it.
In the interwar period and WW2, besides firearms, there were relatively slim pickings for war equipment. Almost all of this equipment was in the hands of the Great Eight and a few others. This really isn't a problem for a good portion of you, being great world powers. For the rest of us, however, we're kind of forgeted over. From a roleplaying perspective, the rest of us have 3 options.
1) We can import 100% of our war equipment (being tanks, planes and warships) from other nations. This is going to align the nation receiving with the nation sending, which can cause issue if the sending nation is dragged into a war the receiving nation doesn't want to be in. Not only that, but if the sending nation gets involved in a war, they will have less equipment to import to the receiving nation.
2) We can ask for the designs of various war equipment from the nations that have them. This still keeps us dependent on the goodwill of bigger nations and their ability to provide, and will likely still align the receiving nation with the sending nation.
3) We can take some of the more obscure designs from great powers and produce them as our own. This is the most favourable option in my opinion. No nations need to be dependent on each other and the worst that is being lost is an obscure and likely ineffective design. For instance, the ship picture I posted on the previous page is a Town-class light cruiser designed by the UK.
I would love to design my own tanks, planes and warships, but I haven't found a entrepreneur My Gun-esque designer and I'm far too inept at lineart to draw a ship. Taking drawings from deviantart is always a good idea but I have my doubts about their uniqueness.