Makes getting the legendaries and epics you want easier, but still difficult.

Nice! :))) Lot of dedication 🙂
And cool idea, but I think filling your collection after an expansion goes live would make bought packs during the last expansion feel worse.
I personally think the solution would be to increase rewards by at least 4 times, to counteract the fact that dusting commons and rares reduces your average gold-to-card-value ratio to 4/1 after getting them all from the first 40 packs.