Is it possible to specify different fare classes/cabins in the different legs of a multi-city itinerary on AA.com? I can't find any way to do this using the trip planner that seems to come up when you indicate "multi-city," which is practically unusable as far as I'm concerned, compared to their normal trip planner.

(Although right now, no matter what kind of trip I select—one-way, round trip, or multi-city—I get this more rudimentary planner that only ever lets you select one class of service per leg no matter what. This seems to happen every once in a while and I can't figure out why or how.)

I found the itinerary on Google Flights originally, and I can find it in both all-economy or all-business, but as far as I can tell Google Flights doesn't let you mix and match either. Is this even possible to do? (I don't imagine tools like ITA would be helpful here since you can't actually click through to book itineraries through it.) I would assume it is possible somehow, since you can book different classes in a standard round-trip itinerary on AA.com. Do I have to call and talk to an agent and pay the phone booking fee?