It does not matter. You can imagine it like you loose your BP node (pool) half of the current epoch and build a new one which will be only available in the middle of next epoch.
So, what does that new node do when you start it?:
- gather all the blocks from peers
- build the current ledger state and other states from these blocks only and nothing else.
Meaning, when your BP node is back it will continue creating blocks as if nothing has happened.
As It was able to regenerate the state of the chain from the received blocks and therefore the new epoch nonce from the received blocks from other peers. Ofc, assuming, KES, VRF keys are the same and/or valid.