The Florida routes are interesting.
AA attempted LAX-TPA a couple years back and it didn't quite work out. I think DL has been on the route for years now. The RSW adds are quite perplexing to me; I don't think anyone has attempted RSW-West Coast service. I never really thought RSW was popular for West Coast travelers as it seems much more a Midwestern market. I can't really see RSW working out in the long run.
AS might be able to make LAX-RSW nonstop service work as the PDEW of RSW-LAX/BUR/LGB/SNA/ONT was 113 passengers per day in the January 2019 - September 2019 time period.
While the PDEW of SEA-RSW was only 54 passengers per day in the January 2019 - September 2019 time period, AS might be able to make SEA-RSW nonstop service work due to
(a) AS having connecting feed from Alaska, Hawaii, British Columbia, Washington State, and Oregon in addition to O&D traffic on SEA-RSW nonstop service,
(b) AS being able to significantly stimulate additional demand from SEA to other markets that were added by AS in the last 3 years such as CMH, IND, and PIT, and
(c) AS already serving FLL, MCO, and TPA in Florida nonstop from SEA.
While AS doesn't currently serve JAX, AS adding SEA-JAX nonstop service is a possibility as the PDEW of SEA-JAX was 100 passengers per day in the January 2019 - September 2019 time period, which is almost double the PDEW of SEA-RSW in the January 2019 - September 2019 time period.
While F9 has less-than-daily seasonal nonstop service to CLE from SEA, AS adding SEA-CLE nonstop service is a possibility with the lack of SEA-CLE nonstop service on a non-ULCC being a huge hole with the PDEW of SEA-CLE being 218 passengers per day in Q3 2019 and with over 66% of the passengers traveling between SEA and CLE connecting on airlines other than F9 in Q3 2019.
I had also previously mentioned AS adding SEA-BDL and SEA-ORF nonstop service as possibilities with BDL and ORF being two of the top destinations that do not currently have any nonstop service out of SEA.