It's not about whether it can be done in general. It depends on what campaign mods you are trying to install. There are some files or objects that are edited to specifically reflect that object in that particular campaign or theater. And if that same file or object was edited to be specific for that campaign in more than one of the campaigns you are installing, whichever one you install last will overwrite the others, and that could break things.
It's entirely possible that the combination of campaigns your are installing could work fine together. Or it's entirely possible that the campaigns you install will completely break each other and be FUBAR.
In general, if the creator of a mod has suggested a dedicated mod folder, it's best to do it that way.
PS - it's not campaign files that usually interfere with each other. It's more when the mod is creating a "conflict/theater specific" mod or install, where aircraft, weapons, and objects have been tailored to suit that scenario.
edit - I just re-read the list of mods you want to install, and I'm pretty sure some files will conflict. There were talks and threads a looonnngggg time ago about creating one mod pack that covered all the theaters, but I dont think it ever happened. I created one for myself, but it wasnt nearly as in depth as all the ones you listed on their own.