Hm, how difficult would you say those unimplemented cards are? Now, they are all above my current abilities, but I'd guess
Synthetic Destiny would be the easiest one, if you can pass numerical parameter to a delayed trigger.
Mizzix's Mastery could be possibly done like
Epic Experiment. For
Grasp of Fate, perhaps something like
Blatant Thievery would work (though not sure why
Blatant Thievery has the "TargetMin$ 0" command when the number of targets is fixed).
EDIT: Looked at Gatherer rulings for
Dawnbreak Reclaimer and it has a corner case when opponents have no creature cards in graveyards. Basically, there are four possibilities when its ability resolves:
1: You have a creature card in graveyard, and so does at least one opponent (the default mode)
Here, first you must choose a creature card in opponent's graveyard, then that player has to choose a creature card in your graveyard, then you get a choice whether to return these two into hand or not.
2: Opponents have creature cards in graveyard, but you don't
You still choose a creature card in opponent's graveyard, the player's choice is skipped since you don't have anything, then you decide whether to return that card to opponent's hand or not.
3. You have a creature card in graveyard, but your opponents don't
Instead of choosing a card in step 1, you choose an opponent. That opponent will select a creature card from your graveyard, and then you choose whether to return it or not.
4. Neither you nor any opponent have creature cards in graveyard.
In this case, the ability does nothing.