Is there any way to add Cortana channel without MSA account ? As I see now the only solution is to add an external MSA account to aad and give permissions to the app than create the channel. You guys have better idea?
Yes and no.
For consumer skills, you can create your bot with an AD account (or host it anywhere you like), but the MSA is required to connect the Cortana channel. So, you can set up a pay-per-use MSA to connect to the AAD created bot and chances are your throughput for Cortana events will never result in a charge!
For enterprise skills, you can't use a MSA! Everything uses AAD accounts. You can reach out via this blog to get on boarded.