Ok, thanks,
My 2 cents here.
1. Set the Theatre, BL5s and BL3s optimally for the Theatre.
2. Daisy-Chain the PLs BST >> BL5 >> BL5
3. Daisy-chain PLs BST >> BL3 Splitter >> BL3s
4. Connect Core to BST (not sure how this is done)
5. Daisy-chain Core coax >> BL5 >> BL5.
You will need to make a listening position for the BL5s stereo only and maybe configure the BR1. The music signal will be digital to the BL5s from the Core and the BST should control volume signal via PL?
Thats how I imagine it. Obviously, I can’t test but hope it helps?