Hi, I’m not Fortnite dev but this is kinda a tricky task that I worked on and somewhat accomplished what I desired. I suggest you take a look at the hierarchical instanced static mesh component.
You should make a system where if the player tries to chop a tree, the instanced version gets replaced with the actor which is choppable. I will explain how I did mine. 
So first, make your instanced component:
Then head into your foliage types and set all your trees to use that component:
Now for multiplayer, this way might not be the best to do this because I’m still learning networking logic however I got it to work as I wanted:
Even though this works as I wanted it to, it probably won’t work as intended with clients that join a session late. For that I believe you must store the state changes in an array since every instanced foliage actor has the same ID on client and server (I believe).
I’ve found this thread which talks on that specific issue and how to handle it:
Anyway, I hope this helps. Best of luck!