Still Confused about One Aspect of FP+. Help?

[nkereina]

The only issue with this strategy is that headliner FP+ might not be available in Epcot later in the day.

Very true, and one of the cons of FP+ for park hopping. The alternative would be to relegate yourself to 3 FP+ a day and book them all for your later park, and get to your first park at rope drop for (hopefully) short stand by lines.