According to unificationist accounts of scientific explanation, scientific explanations are bodies of propositions and/or schemata that unify a large variety of phenomena. But why think that a unification is an explanation at all? Why not think it is just the statement of a universal accidental generalization? And shouldn't explanations of contingent events be causal? The firm unificationist may reject these worries, of course, as question-begging. But a theist who is a unificationist can solve both of them.
God is omni-rational in the following sense: when he strongly actualizes a state of affairs, he does so on account of all the good (nonexcluded—this condition won't be relevant in the cases I want) reasons in favor of strongly actualizing that state of affairs. Unification under a natural description is a genuine value—it is an aesthetic value—and hence that a collection of phenomena can be unified under a natural description is a reason to produce that collection of phenomena. And because God is omni-rational, if he in fact strongly actualizes that collection of phenomena, he does so in part because the phenomena can be unified under that description. Hence, the unifiability of a collection of phenomena, by virtue of God's will, partially explains the obtaining of that collection of phenomena. Consequently, unificationist explanations can, in fact, be expanded into theistic causal explanations while doing justice to their unificationist character, in a way that takes care of my two objections to unificationism.
A theist who rejects Molinism, Calvinism and Thomism about indeterministic events, however, cannot run this line in cases where the unifying patterns are entirely the result of creaturely randomness, as in those unlikely worlds where coins flipped always (it's possible, just unlikely) land heads. In those cases, my story above disagrees with the unificationist, because that the arrangement was all heads is not God's reason for producing the arrangement, since God did not determine this detail. However, it is precisely cases like this which are least plausible for the unificationist.
Observe, also, that the theistic story adds something explanatory to the basic unificationist story. It unifies the unificationist explanations. Thus the unificationist would do well to be a theist. That's the intellectually satisfying way of being a unificationist.