The rather fuzzy
god term that you are using is pretty similar to a popular trope in science fiction, namely that of the Sufficiently Advanced Alien as e.g. seen in Star Trek with the Q.
Such being does not necessarily need to transcend the laws of nature and can still be bound by them. It may be that it only has a better understanding of nature. Or it may have "ascenced to a higher plane of existence" (what ever that may mean).
Especially your statement that:
A 2015 human would classify as a god if brought back to 500bc, together with some modern, battery-run gadgets, firearms, etc
is pretty close to Clark's Thrird Law:
Any sufficiently advanced technology is indistinguishable from magic
And Michael Sherner adapted that statement into:
Any sufficiently advanced extraterrestrial intelligence is indistinguishable from God
I am not aware if there exists a label for this kind of theism, yet a few religions and sects and other esoteric world views have include this way of thinking at least to some degree.
A current one would be Mormonism whose believers claim by its doctrine of Exaltation that "human beings can grow and progress spiritually until ... they can inherit and possess all that the Father has—they can become gods".