They wouldn't have to charge too much more for a 10 day capped annual pass.
The correct comp, in my opinion, would be the cost of 2 separate 5-day tickets at the cheapest. But also 10 1-day tickets would be an appropriate comp. Comparing to a 10-day park ticket doesn't really apply because if you're looking at a 10 day annual pass instead of a 10 day park ticket, that means you are planning at least 2 trips.
Two 5-day park hoppers is going to cost you over $1,200
Two 3-day park hoppers and a 4-day park hopper will run nearly $1,500
Ten 1-day park hoppers will cost you over $2,000
You could sell 10 day annual passes to out of state guests for $1,000 and secure a lot of repeat business without overwhelming the system with too much use.
Florida residents already get 40% off 4-day tickets and 30% off 3 day tickets so you'd probably have to go down to about $800 to get people on the hook for a 10 day pass for
DVC/FL people. Or maybe you just give them more days for their $1,000. Either way I'm pretty sure you'd have plenty of takers.
10 days may be too small, though. Maybe you could go for 15 days and bump it up a little price wise.