I finally managed to beat this. Chapter 26 was a pain in the ass, and it also took me a while to figure out chapter 27, since I didn't realize I could deploy units in the upper part of the map initially.
This was a very challenging run, though I'd be lying if I said I still remember most of what I did in the beginning, since it's been so long. I just know that the pegasus knight talent was definitely worth it, as Falcon Knight Silas was my MVP. Kaze was a very good combat unit, and Nyx also helped despite not seeing much combat. Jakob fell off really hard, but at least was still a 8 move shelter bot. Charlotte was mostly Kaze's pair up, but I really messed up by not getting her to level 5 on one of the free paralogues, Rally Strength would have been a great help.
Anyway, my final turncount was 129 turns
Here's what I did on the final chapters: