That sounds really fun. It always seemed like a hard problem to me, like how do you give the player freedom while also providing a narrative/storyline which, by its very nature, is restrictive. What you've seem to done is (and correct me if I'm wrong) break it up into two parts. The first being a sort of sandbox-like environment with discrete quests/stories (the freedom part), and then afterwards the player chooses and enters the main storyline (the more linear restrictive part). Its a really interesting approach.
That said I'm still very interested on how you would implement the first part and all the systems involved on a technical level though.
One thing I hate the most about linear/branching stories is the restriction that comes with it, and not being sure how much content did I really miss and having to replay the whole thing and just make a few choices differently to see that.
Its going to have a lot of limitations due to the rpgm system (I still need to find which version will best suit my needs) but ultimately its going to probably hinge on writing my own plug ins to utilize switches and if/else nests. for instance, all quests will be flagged as available, but as the player approaches and receives such quests, the player's choice to accept/decline will turn flags for that quest on or off (each quest linked to a kink). As more quests are fufilled, then a secondary set of variables for that kink comes into play, that will utilize a scoring system+fame system to determine how much you are involved in said kinks/fetishes. Each NPC (yes, I'll have to customize and set multiple dialogue groups for each NPC) will switch to certain scripts with generic responses that cater to the player. The script itself will utilize the flags and variables that are accepted in. Example, lets say you've become famous for foot worship, but also somewhat known for being into smells/sweat
an encounter will begin with a boot cleaning/licking, then when your sweat/smells variable is >= to a certain value, it will add in a line how you intake the aroma of her stench, the fact shes been walking around all day really turns you on. from there the NPC will comment on your enjoyment of her smell and may request you lick the sweat off her thighs/calves, which you can do or deny, leading to a +/- in that category depending on answer. As you get higher numbers in a variable, the more likely you are to see this additional text and dialogue, and the NPC will determine whether they share this information or not, increasing your fame in that fetish.
^this is an absolute batshit amount of variable and nesting, this is why I probably will never release this until its actually almost done/is done, because waiting for all that to be coded would be a nightmare for people. I just wanted to see if this is something people are into and worth the amount of time and effort it will take me to put this together. I can't think of a more efficient method, as such each npc/love interest is going to have multiple scripts that they have to select on based on hidden stat scores. I did find a plugin to start that process to track all these variables, the idea is to take it further than where it currently is. If you're interested, this is the plugin I intend to change/adapt around this whole system with kinks/fetishes:
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Edit: If you're a completionist, you'll absolutely hate my game then, the only thing you can do is accept and do absolutely everything (which is not what this is going to be intended to do, its intended to tailor to your unique interests), then save before every love interest route and play through each love interest separately after you finish all the earlier content. Even then, its not possible, because I've already decided some girls will react/change based on some things you are into/not, if you accept everything, you'll turn some of them off, and then you're not necessarily on a "good route" but a "bad" one with them. Just because you accepted and chose someone, doesn't mean they accepted you, you can have a neutral, good or bad ending with all of them. I said this earlier, but some girls if you choose them, depending on your choices and actions, might actually dislike you and make their whole purpose of accepting you to ruin your life. (not a happy ending)