You mentioned feathering out the finish to prevent cracking, but you never mentioned actually glassing over it after its done....Would you glass it or just epoxy it since Im basically just replacing the old glass back in its place?
If your deck core isn't rotted away or wet, but just delaminated from the fiberglass skin- then just filling with epoxy will be a permanent fix, without any glassing.
If the deck core has been left flexible long enough, the flexing can fatigue crack the fiberglass under and over the core. In this case, you'll need to re-enforce these cracks with new cloth, especially from underneath. On my C22, one of the cockpit benches would flex like 1" down when stood on, and I found the fiberglass underneath the core cracked through. After epoxying it back together, and covering the crack with new cloth from underneath, it's good as new.