They can NOT copy other characters, Mass Effect is own but EA. The last thing StudioFOW would want is a lawsuit from a huge company, similar to what Riot Games did to Mobile Legends. Secondly Mass Effect is an actual game whose sole focus is gameplay and story telling, you can't not compare that to a smaller adult game. The sole focus is the adult content, which gets higher priority over gameplay. Subverse already takes long being a smaller game, rebuilding gameplay exactly as Mass Effect is a much longer and unnecessary processes.
Anyways yes there are many similarities, for example the "Imperium" is a parody of the "Presidium". In Mass Effect its located in the "Serpent Nebula", in Subverse its the "Dragon Nebula" similar naming scheme.
The Sexbotts are A.I that went rouge, the Geth were also A.I that went rouge, instead of killer A.I, its horny A.I lol. Captain is a veteran on the Mary Celeste, Shepard is a veteran on the Normandy. Lily is a scientific researcher, Mordis is a scientific researcher, Fortune is the an elite hacker that can hack anything, Kasumi is also known to hack and infiltrate anything, DEMI is the Mary Celeste's A.I, EDI is also Nomandy's A.I, Killi is has Vannaren whose race has an extreme desire for sex, Wrex and Grunt are Kogan whose race has an extreme desire for violence. Even the "Devotion" system is an inspiration of Mass Effects "loyalty" system which StudioFow addressed themselves :3