Amit, could you please clarify?
1) How are you going to split Maestro for External/Internal?
Security groups or Virtual Systems?
2) Are you going to use tight ACI integration?
I mean are you going to use one-arm External Maestro security group or VS configuration and redirect traffic to it using ACI Contract + Service Graph (L3Out)?
Or are you going a traditional way (and in this case it is not so relevant you are using ACI, though you still can ingest objects from ACI for identity-based policy)?
Same for Internal.
My personal opinion:
- for External you may use either L3Out integration or a traditional routing
- for Internal I'd suggest one-arm configuration with full integration. In this case you do not need to change customer's topology For him it will look transparent, as he expects from bridge mode. Cisco will take care on redirecting traffic for the inspection to one-arm'ed Maestro.