The main thing that I've been curious about is how folks address the fact that these things are physical documents, even after they are used for Cover experience. What happens when one is damaged or destroyed but you've already "cashed it in" to make a Cover? Do you suddenly lose your dog / significant other / job / what have you?
One thought that I considered myself was making the pacts operate more like "vouchers" than anything else. For the mortal making the deal, the benefits take effect immediately but on the Demon's side it doesn't actually do anything. Yet. Able to be redeemed for (x cover element) by any given Demon once but when that happened, they were no longer valuable in their physical form. The cover is established, demon magic used. Basically this avoids a lot of mechanical confusion of what happens and also makes it so a demon player doesn't need to keep track of binders of pact information both IC and OOC in order to play the game.
On the story side, it allows for things like "buyer's remorse" on the part of the mortal and it allows the Demon to cultivate mortal elements so that their covers aren't just piles and piles of horrible things and bad decisions.
Demon Michael and Mortal John.
John is having severe issues with most every element of his life. He's broke, jobless, and his ex Jenny is a crazy stalker who hates him.
Michael goes over to John and offers to solve them in a single fell swoop. He will solve the job problem, solve the money problem, and in time, he will take John's relationship with Jenny though this will take some time. (Mechanically, adding merit dots to John, adding cover element (Jenny)
John's fine with this. After all, all they do is fight. And if Michael can make the rest happen, he'll be a happy camper.
So the deal is made, John's benefits kick on immediately and at some point in the future Michael will come for Jenny. The only thing he's not allowed to do is forget about her.
Now here's where the fuckery comes in. Before he comes and claims his due (adding the Cover) Michael goes to work on Jenny. Over the next couple days, weeks, months, however long, he solves their issues, gets them back together, fixes up their relationship to the point where it's thriving and golden.
At this point, Michael has a cover contract for a thriving and golden relationship with Jenny. Still not worth much in the cover department (original values hold) but that's not the point.
At this point he can call it in, sell it to some other Demon (Cover element that's not inherently crappy?!?!?! Yes please!!!) or go back to John and see if he wants to renegotiate.
It's much easier to explain in person so I don't know if I'm saying this right in this medium but hopefully the basics at least are conveyed.