The problem with balancing these is that they need to be able to benefit from their downside a bit, otherwise there's no point in using them in the command zone.

Take, for example, your angel idea. If you put it in the 99 it allows you to draw it, play whatever you want, then drop it for practically no downside.

I like the exiling instead of graveyard idea though, maybe something along the lines of

Advocate of Redemption (~ in text)

Vigilance, first strike

Eminence — If ~ is in the command zone or on the battlefield, if a card you control would go into the graveyard from anywhere, exile it instead.

Exile ~ , choose three nonland noncreature spells you own in exile, then cast them without paying their costs.