I am working on a cake that I was going to do the entire thing in a fbct, but looking at the design I think parts of it are to small and intricate to look good as a fbct.
So my question is can I make the background bc and add RI transfers on top of the bc, or will the bc break down the RI?

I'm thinking I can do the details more accurately in RI (fairy, swords, words and scrolls), just worried that they will hold up on bc.
Thanks in advance for any and all help!

Buttercream definitely breaks down Royal Icing. Could you use a really small tip and some smoother buttercream to do the details?

<...Buttercream definitely breaks down Royal Icing...>

Wellllllll yes and no. If you wait until the b'cream has crusted you can use RI on it. They might soften some but should not turn into a puddle of icing