You're right - both Edelman and Tate can play slot or outside.
You're also right that Amendola and Edelman were somewhat complimentary, except that Amendola is primarily a slot receiver.
I loved the Amendola signing, by the way, but he was nowhere near the level of Tate. Amendola's best year was 85 catches, 689 yards, 8.1 average.
Tate?
91 catches, 1331 yards, 13.4 ave. Tate's been over 1000 3 times, over 800 multiple times and put up almost double Amendola's yards in a slightly shorter career.
Amendola fits the offense. So does Edelman. So does Hogan. So Does Dorsett. If Edelman could be on the field with Hogan and Dorsett last year, I think there's room for Golden Tate and Jules to run around each other out there.
But no, i wouldn't pay 10+ for Tate, personally, and certainly not 15.