yes, but its cristal clear that such a system is sequel material and not expansion material. better stick to "realistic" suggestions :sleep:
In my opinion it could be done quite easily as follows:
1) You as player build the brigade as usual, but what you build is only weapons, trucks, etc.
2) Once build the brigade you have the ability to put it in a pool (training pool) and then it is slowly formed (soldiers are trained). After some time (6 months? 1 year?) you can deploy the brigade.
3) If you don’t put the brigade in the training pool you have only weapons that you can ship/delivery to any country you like. Who gets the weapons can train the brigade.
This will mimic very well some divisions equipped with foreign material and has the potential to better control military production. For example for some countries it will become impossible to produce capital ships just because they have researched the required tech. Still nowadays many countries cannot produce tanks, airplanes or even "small arms".