Funny thing, but recently I was thinking about combat implementation in RenPy and came to an idea of a minigame that should work (in theory). In Milky Touch (another 2D VN Wildquill worked on) there was this lockpicking minigame:
Nothing fancy, you just has to click at the right moment, when the swinging slider (the orange line) is right in the center. The catch is that the slider moves fastest when it goes through the center and slowest at the edges of that, eh, hourglass thingy. I saw a couple of very similar minigames in other projects. So I guess, a shooting minigame can be very similar to that concept. I can see three variants of its implementation:
- The simplest one is that you enter the minigame and have to click at the right moment etc etc, and your every click is a shot. The closer to the center the slider is, the more powerful your shot would be (dead center would be like headshot/critical hit), while edges would be a miss/grazing shot. But while you're taking your time aiming, your opponents shoot at MC all that time, so the longer it's taking to kill them the more health you lose, up to MC getting killed and you losing the minigame and having to load a save.
- An easier variant would be turn-based combat. Same as above, but while you're aiming to click, time is frozen for your opponent, so there's no pressure to end the fight asap. After your single shot, your opponent makes his single shot, dealing some damage to MC, after which the control is returned to you again, and so it goes until either MC or his opponent NPC is dead.
- A fancier variant of the above; dividing each player turn to two phases. In the first phase player would chose the opponent's bodypart to aim at, like in Fallout 3/4 V.A.T.S. The second phase is taking the shot itself, and it's one of the above options - either turn-based or real time. Except depending on the bodypart chosen effects from the critical hit would wary. If it's the head the opponent would be killed immediately; if it's arms, a critical hit would lead to opponent getting his weapon shot out of his hands and to his surrender or an escape attempt (so a non-lethal option); if it's legs, the opponent won't be able to escape, etc etc.
Of course, this simple base can have a multitude of mechanics to raise the gameplay depth. Multiple opponents at once, different classes of opponents (like heavily armored guys for example), different weapons including non-lethal, different ammo, full auto fire (one click gives a hard-hitting barrage), healing/shield consumables, having to reload when out of ammo, utilizing some skills (like throwing a grenade for example) instead of just shooting, etc etc. On other thought I probably went overboard here, since Sunwave Hotel isn't exactly Tarkov.
PS: Minigames aside, I strongly suspect that transferring a game of SH size from Unity to RenPy in the middle of development might be an unfeasible task.