Depending on where and when you're flying, I've found the 15K points threshold for Mosaic comes much faster than actually doing 30 segments and 12K points. Since you're in S Florida and would prefer not to do 'turns' on Transcons to boost earnings, then I would book a refundable fare. Refundable fares from S Florida should get you to Mosaic pretty quickly.

Absent status matches, which B6 hasn't offered in a long time, to qualify for Mosaic you need to spend the $$$. There isn't an easy way around it; just like DL's and UA's revised programs.

Agree on the change fees waiver though; that is by far the best 'perk'. Dedicated customer service line is great too.