If it can be managed cleverly and respectably, than tech updates can be done. If there is any hint or sign that it might be done for self-advancement, it shouldn't be done. 

And this is a ridiculously narrow window for me. VX was acceptable because it meant a brutal alternative to nuclear weapons that came with its own moral questions, horrible scenes, and flavor. Aaron's spy-plane is acceptable because it means you get these almost-impartial godlike commentary on shit going down around the world. Hug's massive zeppelin aircraft carriers were acceptable because they were unique as hell and gave Prussia an air of power without using cliches. The limited jets are acceptable because, partially due to how few they are, they put some weight behind the images of China and Spain as the only superpowers. This is the criterion for acceptable tech updates. They have to add something to the spirit of the thing while also making sense. If it all breaks down to "I should have jets because it is possible if you think about it." Or "I should have jets because it will make my country look cool." then I really don't think you should be given that sort of tech.

The worst thing you can do is start out by trying to simply show off how important or bad-ass you are, because then nobody will give a shit. In the past we let people have a little more breathing room in these things and they responded by fucking up the cannon with the least interesting storylines and characters they could pump out while just jacking off about how important they must be because of all their tech and borders. Now we know better and we restrict these things more. Make something without crazy tech and maybe later you will be allowed to do some crazy tech.