I think the DFRPG system could definitely handle C:tL. I really love Changeling the Lost, but I haven't played it in a long time because FATE mechanics are just so much better. If you want any help converting the system over, let me know! I'd be happy to lend a hand.
I think Pledges could probably be handled with aspects - when you make a Pledge, all parties to the Pledge now have that Pledge as an aspect on them. That Pledge could then be invoked (to represent boons granted, glamour gained, etc.) or compelled (to represent favors/tasks/alliances you've agreed to) just like any other aspects. Breaking a Pledge would probably give all other parties to that Pledge a free tag on the Oathbreaker's Pledge aspect.
For Contracts, it really depends on how you want to do it. Perhaps pick some appropriate stat and have it determine how many dots of Contracts someone can have, and have another stat determine what the highest level of Contract you can use is? Maybe charge Refresh?
Talecrafting actually works remarkably well with DFRPG - when you're Talecrafting, you're basically just declaring an aspect on the scene and then invoking it for effect.
I don't remember as much about the Hedgespinning system, but it could probably be handled like a thaumaturgy ritual in that you would need to spend time gathering the right ingredients etc beforehand. Only you'd likely be rolling Crafts instead of magic.