This is a good post.The problem with special projects is time. Sure, motherships are considered OP by many players, but are you really going to be using them in your games? That depends a lot on what you are doing in your games.
This means that there is a lot of context to what special projects are actually useful. This extends to the point that I've gotten tired of some games before I could get things like fleet nuclear subs with SLBMs in action. Nice techs, but I'm not running the clock for that long just sitting around waiting for the projects to finish, then the ships to finish, and so on.
As another example, I consider flame tanks to be just about always worth it. But part of the reason is that most countries start out being able to get that project into place the moment they get their first breakthrough. And you can produce the flame tanks on IW hulls if you want. It's not like you need unlock 1940 mediums or 1939 artillery to get them to work.
I played Italy to test the new GtD dlc research options earlier this year, and you get an aviation research facility by focus, and you can get it very early, but Italy needs to build all the other facilities from scratch. Civ factories are very limited.
This means radar and helicopters are quite easy to get before the war, but you need to sacrifice a fair bit of civilian factory production to get flame tanks.
Armored vehicles breakthrough comes after the war starts, I guess there’s a way to work out how to get it earlier with how everyone is talking here though.
…and if you want flame tanks AND cruiser subs before the war, good luck building enough infantry equipment and support equipment for your units. (At least that’s what happened when I tried to acquire all four research labs as soon as possible, so I clearly need to work out a new “optimum” build sequence to maintain my basic kit production.)