Thanks for you answer!

The point of what I want to do is, I want all MX rifles and ammo to be swapped without having to edit missions themself. Like a total (well, partial) conversion mod, so an addon/mod version would be ideal.

By studying El_Guiguitre's RHS replacement, which does exactly that, but with RHS assets, I found out that they did it differently than how I wanted to do it originally.

Instead of overwriting default loadouts, they basically overwrite all the mx classes and replace its properties and assets, so that when, for example, arifle_MX_F is called, an RHS M4 appears. At least that's how I interpret it. But it's quite hard to edit this mod, because it's too cluttered with other stuff like vehicles, all the gear and so on, to be easy enough to read as a complete beginner in arma modding.

My line of thought right now is; I have to figure out how to reroute assets and change properties. Maybe I can copy the contents of, for example, the arifle_SPAR_01_blk_F class and paste/overwrite the contents of the arifle_MX_F class. Any thoughts on this?

I'd have to overwrite the MX magazin classes too, but since they are unique to the MX series, it shouldn't be an issue. This means after my config.cpp is loaded the original MX assets are not referenced in cfgWeapons at all anymore. I think this would be a rocksolid way to literally replace it anywhere in the game.

Any help, thoughts or ideas are welcome :)