I'll just move btc after the split to a new address and then export the keys of the then empty btc addresses.
Remember to empty your entire Armory wallet of BTC before you export private keys to something less secure. I am 95% sure that if somebody gets two private keys from the Armory chain, then he has them all. And if somebody has just one private key, and the chaincode
which is unencrypted in the watch-only wallet, then all following private keys are compromized.
Make a new wallet in Armory and move BTC before the split to it.
After the split move BTC to your normal wallet again.
Then export the key from the tmp wallet and move BCC.
Thats how i do it.
Once done the tmp wallet will be deleted.