In D2, I was happy to have some characters focused on Gem collection, some characters focused on Rune collection, some characters focused on Socketed Item collection, and so on.
That kind of leads to repetitive, one way gaming.
His(/her lol) idea, sort of like having a locked Item is cool because it's more random and engaging to me. Looking for gems, runes, gems, runes was dull to me.
Anyway your idea with the 'Contract' thing could work fine but here's how I'd imagine it'd work, which is slightly different in that it's not scrolls.
I find this Uber epic Axe for my Barb, then I'm like, "Wow I found this Uber Epic Axe for my Barb!" I read it. Says "Kill 150 Fallen Imps with this Blank Axe" and woosh! the magic attributes appear.
Example of the Uber Epic Axe:
Locked* Hand Axe 100-200 Damage
average 120 damage per second
Sell value 35000 Gold
- - - - - - - - - - -
Locked* Attributes: + 170-340 Cold Damage
Freezes Target + 3
+12% Extra Experience per Kill
+20% increased Attack Speed
Required to unlock:* Kill 150 Fallen Imps with this Weapon
122 Fallen Imps Killed with this weapon.
28 Fallen Imp Kills remaining
* There are better words than 'Lock' But too lazy to think of one.
Unawakened?