For my Economy SFO-LAX-LIM-GIG redemption on Alaska and LATAM, I noticed that First is now available for redemption (at the lowest mileage tier amount) on Alaska from SFO-LAX and Business is now available from LAX-LIM. Only Coach is available from LIM-GIG. I don't mind spending the extra 20k miles for Business even if LIM-GIG doesn't eventually open up in Business.

If you search the entire one way (SFO-GIG) only Economy redemptions show as available. But if you search LAX-GIG then Mixed Cabin itineraries appear showing Business from LAX-LIM and Coach from LIM-GIG. Business apso shows up if you search LAX-LIM by itself (and Business shows up if you search SFO-LIM (via LAX)).

The strange thing is that the Alaska feeder flight from SFO-LAX has First saver availability (at the lowest # of miles, not the higher tier First redemptions), so I'm not understanding why the Mixed Cabin option doesn't appear for the entire SFO-GIG itinerary.

Is there some rule about that prohibits mixed cabins on LATAM when an Alaska segment is added? Seems odd since there are 2 Alaska options available to connect using the lowest redemption tier for First (and that show up if you look up SFO-LIM).

Can Reservations just reissue the ticket and collect the additional miles and rebook as a mixed cabin itinerary?

And assuming they can, if Business opens up can they reissue again either before or after travel commences?