I would say make a hell map. Like literally, hell. Like Lolcano a bit, but not terrible for ph. We've been needing a saxtonhell themed map.
Also if you do make a map plz make the blu spawn out of view from the hiding props and put the invisible walls high enough to let soldiers fly around. More than one type of prop types and areas for them to hide (enviromental props, office props, construction props..etc) and multiple levels would be nice for the parkour'ing. Like maybe using bridges like canyon does, it would fit the theme.
But yeah a hell themed map would be my suggestion, with lots of big rocks, some lava, in a big open cave, basically like a heavily modified lolcano.