No. Mods can not simply be copied into the game files. Each patch, every single change has to be manually replicated on Relic's side. Which is one of the reasons the live patches can take so long to make.
While that's pretty much expected (mods aren't patches); would "test mods" improve the working and/or iteration speed of official (and preview) patches?
For example, let's say there's some change the balance team and/or community wants to make - for the sake of discussion, nerfing the M36's moving accuracy multiplier. Chances are, the first value anyone tries (mod maker or balance team) won't be the 'perfect' value; however, a mod maker could iterate changes much faster than the official preview patches. For example, on Monday they could try 0.6, on Wens 0.5, on Fri 0.55, etc. With much faster iterations, we could figure out what the ideal value (or close to it) is quite quickly, and then the balance team could implement that value.
This could prevent issues such as the perceived under-performance of the IRHT, which was only iterated on (publicly) twice, before the final release.
This would, however, require excellent communication between the balance team, mod team, and community; the mod team and community would need to propose ideas that are possible to implement by the balance team (so no ST animation changes, or changes to every infantry squad), and the balance team would need to share their ideas with the mod team ("we were thinking of trying X for the next patch" and/or "the scope of the next patch is Y").
Effectively: Community made test mod -> official patch preview mod -> official patch