An interesting idea although it goes against the themes I want to run with this world where the gods are both angels and devils in the same person. If you feel like it, it would however be interesting if you would post it and let us see the fruits of your labor.
Well the short of the idea is essentially That each God of whatever the hold dominion over has a counterpart devil, and vice versa. Numbers aren't decided, it will be at least twenty, but with some of the specificities we've set we could easily end up with like 400 (hopefully it'll never reach those numbers). If it was to stretch into triple figures for them, naming wouldn't technically be an isue anyway for the following reasons. The realm of the Gods and the Devils respectively, are both completely reachable by mortals. If you make it to either realm you automatically gain the title of a Godhood/Devilhood, this is something that is just understood by the mortals of the realm. However, tey both pose completely seperate but equally grueling challeneges in terms of reaching them, and it can be all in vain for most that achieve it, as becoming a God isn't as the mortals perceive it.
Most Gods tend to be sort of free agents, they don't have dominion over anything, and are basically immortal peasants in the grand scheme of things, each that rules over something has a seat in a sort of grand council type setup, but at any time a free agent god can challenge a seated God for their position. If the challeneg is okayed by the grand master ('The King God' as a working title) allows the challeneg then both the challeneged and the challenger must commit acts within their respective dominions (for God of War they must both create some form of war), and the other seated Gods wil vote on who commited the better act within the dominion based on different factors (e.g. the scale of impact within the realm, in comparison to their actual direct influence).
The Devils seats are treated in much the same way.
That's sort of the basics of it, there are more complex elements to it as well that are still very much in a conceptual stage.