1) during NSFW animations you will have a button to "impregnate", this leads to a bonus animation + a mini game (we can brainstorm what kind of mini-game) that will make the player pregnant.
2) rewards after the scene - > I was thinking since currently when you press "F" a parasite spawns, maybe if you are preg and press F another kind of parasite (or 2-3) might spawn depending on which enemy character got you pregnant, then the belly size is decreased instantly what do you think?
a) how long do you think the preg state should last if we dont press F to spawn the creatures?
If there's a button you can press to effectively terminate the pregnancy this becomes much less relevant. Although I suppose if you could carry certain things across levels it could create a pretty minor balancing issue or exploit (i.e. carry a flying minion into a level without any flying minions available, fly out of the map, and skip the level, or something like that). I dunno how in-depth you're gonna make the system though so maybe that's just not a concern.
In any case, it should probably be related to your expected playtime for each level on average. Like, if you expect a level to take about 30 minutes to go through by Joe Shmoe, you might make the birth happen automatically at 15 minutes or so.
But you could also just make it permanent, if you don't press the button, and not transfer levels. Then if someone's more into pregnant sex than impregnating sex, they can have the former without as much of the latter.
b) also should she be preg during NSFW scenes or only outside (I mean sex while prengnay)?
Pregnancy locking you out of NSFW scenes, or worse just evaporating the minute something tries to screw you, would probably be bad. I definitely think it'd be worth adding some pregnant sex, even if it's a more limited system (and as you said, this is biopunk, so it probably should be a more *expanded* system if anything.)
c) should you be insta - kicked out of the NSFW anim when you got preg?
Probably not, although I might delay getting pregnant until the sex is completed, or at least getting visibly pregnant (so the same animations can be used all the way through).
d) any specific idea about the preg-fetish that I missed in terms of animations, x-ray etc, or anything else..?
I mean different people will have different preferences and things they want to see, obviously. For example, the hottest thing for me is seeing the fertilization occur. I also like the idea of the girl feeling it and cumming her brains out (even in non-con), despite that being physically impossible and extremely stupid.
I think if someone's into X-ray it's probably safe to assume they want to see the fertilization occur, so some sperm-enters-egg sequence would definitely be included under that option. I would also separate
pregnancy fetish and
impregnation fetish in your head. Some people just like the already pregnant girl, some people like impregnating the girl but don't care for the look of a heavily pregnant belly. Some people like both. So you gotta account for that. Most people are at least fine with both though.
e) any other ideas and about mini games i'm here to listen?
I could see something being done about inducing ovulation or letting the fertilization go through. I dunno what it'd be though. Too many minigames can take the player out of the actual action, which is especially deadly for a shooter like this. The sex already kinda butts up into that despite being the reason most of us are here.
So while I could suggest some minigames, I don't think they're a good idea to implement. Maybe just some items to tell the game "I'd really like to get knocked up soon" or "I'd really like not to get knocked up for a bit", for circumstances where someone is for whatever reason really not feeling the fetish today (but doesn't want to turn it off in the options)
3) as this mechanic will be optional, giving some rewards like a modded ability or perhaps more loot for a limited time, it won't be tied to the story. There's also a deathmatch (boss war) game mode, where the mechanic should also be present, so I'm calling for not making it story related.
4) should there be any downside if you use and/or fail to use that mechanic, basically the pregnancy going wrong?
It sounds like being pregnant is more like a timer and then when you birth it, the pregnancy goes away and you get a minion. Which is already more mechanically than a lot of impreg games.
I don't think adding miscarriage or something will add anything to the game. If you mean failing the minigame to get knocked up in the first place, then I think just failing to get pregnant is punishment enough. Maybe make it a once-per-sex type thing, so failing means you have to leave the smut, down another enemy, and hop on.