hm, well, it really depends on how much you want established mythologies to play a role in the narrative of your roleplay. For example, having Hades as the mayor implies that his brothers are also kicking around somewhere, as should the rest of the greek pantheon. These characters already have established relations and histories so these would have to come into play with how the characters act in the rp (for example, it woudl be odd for the mayor to be a womanizer if that is teh kind of character you wanted to write, since canonically Hades as a wife named Persephone and the whole 'sleep with anything' shtick is more Zeus' thing). This isn't necessarily a bad thing of course, especially if you're planing on having characters from multiple pantheons interact since then you can play with their existing inter-relations, and how that would make them react to each other (like having Thor and Hercules be sparring buddies, and Thor always wanting hercules to go out and drink with him, but hercules refusing because he remembers hera manipulating his mind and refers to always stay in possession of his mental faculties, small example).
so it comes down to whether you want cerberus to be a 'blank slate' kind of city where anyone can bring in anything from any myth and just have it work because the city is kind of neutral ground for all thinsg supernatural. Or if you want cerberus to be a mosaic city that IS affected by existing myths, alliances, gods, etc. but who all come together in a social mish-mash. The first option lends itself to more player design if you have a creative crew that likes worldbuilding but can also feel flat and directionless if no one really wants to add anything to what you;re giving them to play with, which woudl reqire a much more hands-on approach from you as a GM as far as guiding the RP's story so peoepl don;t get bored. The second requires a lot more prep-work, figuring out how all the different mythological personalities work together or against each other, deciding their social interaction in the city and how that affects the more common residents on a general level (for example, maybe there is a quarrel between the hindu and greek pantheons, meaning that naga/gorgon couples are usually frowned upon) but by such your world feels more concrete to your players so they need less hand-holding during the actual play since they have a rough idea of what they shoudl and should not do already. It comes down to really where you want to put more effort, the set-up or the execution.
If you are gonna go with a more Neutral Cerberus as opposed to a cultural mosaic though, then i suggest not having anyone from canon myth as the mayor, just create a generic demon-lord or whatever OC that acts as the boss, that way you;re not 'colouring' the experience by affiliating your city to any specific myth. If you'd rather not create a completely new character, then try picking a smaller name than someone like Hades, maybe someone from a lesser known myth/religion (like angra mainyu, the mezopotamian personification of the world's evils for example), someone that yoru average player will have less of a concrete idea of what they should already be like in their minds.
there isn't really an overall right or wrong way to do it, just that different methods are better at telling different stories, so it all depends on the theme you really want to go with for your RP.
