'Beauty is truth, truth beauty,—that is allI think any explanation of the nature of the universe should be elegant and the simplest possible solution to the problem (so it could actually be quite complex, whilst still being the simplest possible explanation). Physicists often talk about elegance and simplicity as criteria for their theories about how the world works. Also I think we should distinguish between theories (large bodies of complex reasoning backed by copious amounts of evidence) and hypotheses (propositions about how the world works that have yet to be proven).
Ye know on earth, and all ye need to know.'
~ John Keats, Ode on a Grecian Urn
Theological explanations should also be internally consistent and logical (even if the logic is different from conventional forms of logic), as well as consistent with the fact that there are millions of people with a different explanation. Pagan theological formulations usually take into account the plurality of religious beliefs; Christian theological formulations signally fail in this regard. For example, most Pagans say that other people are following their own unique spiritual path in their own cultures; there's no drive to convert others to Paganism (Jews and Sikhs also believe this). Most Christians believe that Christ is the only means of accessing the Divine, and many believe that non-Christians won't be "saved" (this fails to explain why other faiths are so satisfying for their adherents). Theologians should also practice triangulation, comparing their explanations with those of other religions and philosophies, and with science, to see if they still make sense.
Many theologians claim that theology is resistant to logic because the Divine is paradoxical: but paradoxes can often be resolved by looking at the thing from a different perspective - like the old chestnut about "God is no where and God is now here".