With the tech he's shown he might be able to have pregnancy down to say 15 days though logic wise it's hard to not think the women would notice that they are pregnant in their day to day life.
It depends on who we are talking about, for example Terra now lives with Lex and Vixen who directly suggested it, and in the daytime she will think that this is John's work.
There are also villains...
But although Lex said that it would be a crime not to pass on his genes, if you introduce it now, then you need to justify at least a little from Lex's point of view, and with this in mind the idea of Galatea comes into my head, Lex in the game more than once wanted to have a squad of loyal and capable soldiers, Galatea herself proposed a similar case, there will be no problems with stealth and Lex will get the desired soldiers in the future.
With the "incompatibility" of DNA, taking into account the capabilities of Lex, there will be no problems, and most of the characters can be left to the very end.
By the way, regarding the second unlocking function for the heroines, I think it will be something like unlocking the "night" memory and completely switching over to Lex's side.
There is animation, but the quality of some animated scenes can be called the maximum average, but the art is very good, the style is perfectly conveyed.