If taking ideas, it might be worth implementing the "good vs evil" + happiness mechanics the original game had, but make it more like "motherly wife that loves you, vs abused monster breeder" or something like that.
Like, all the "motherly" tools would be things like kisses, handholding, an impregnation tool, hand-milking, gentle tickling, maybe clothing and accessories, and rubbing (cocoa butter?). Any tools that advance her pregnancy/milk are slow and gentle.
All the "abusive" tools would be things like tentacles, milking cups, ovipositors, grabbing (+throwing) her, restraints, various pumps to overpressurize her womb (cum pipe?), whips, various hormone injections, or sending a monster after her like a minotaur or something (though this might be dumb because it'd need actual animations). Any tools that advance her pregnancy/milk are fast and painful.