I personally would not mind if they added because in most mmo games (I am aware warframe is not counted as mmo rather coop-looter shooter) there are gender and other custmization options and this would be only a cosmetic one once you have a warframe you could use the another body type. Originally they wanted to go for it and some warframes changed gender during the development (mag, nyx (female excal), ember) also concepts changed genders too like zephyr who was originally a male frame. The rescurces was not available back there because the studio struggled and tried to survive so they later when the game kickstarted back into the life dropped the idea because they decided to go for a lore written to each frame and they ended up building a wholly different story what originally the game meant to be. Nowadays it would be tricky to do this and some stuff needs to be redone if they would go with the idea. Still I personally support the idea but the chance to happen is low but as deluxe or special skin I think it is achievable all depends on how many person can work on the warframes itself. The only drawback here is not the lore itself, retconning is a thing in video games but the profitability. They could not sell the same thing twice so for profit wise this would not be a good idea for them. Unless they add mod support to the game like other coop shooters (killing floor comes to my mind or L4D) where there are mods to enchance your experience and not ruining others game because it is more or less local. Warframe in this part more strict because needs constant online presence to play it. This is mainly for security reasons so no one could pirate the game and they can sell platinum.