Thanks for your interest !
In terms of timescale, I have little experience with how long it takes to develop a game, even mostly text-based ones. I've been writing and brainstorming ideas and potential content for the past three years, treating it as a long-term side-hobby. Ideally there would be regular updates to add and improve content, until the various storylines get concluded and inspiration runs dry for secondary content.

As far as mechanics go, I'm trying to keep it fairly simplistic : Character customization, travelling system using regional maps, choice-based questlines and dialogue interactions with NPCs, as well as a few real-time classic stats like Fatigue, Hunger, Resistance, Lust, etc. For the combat system I'm not yet sure, but I'm open to ideas !

For what I'd want in the game : a day-night cycle and a working clock (maybe a season cycle) would pair really well with the travelling mechanic. Various quests and missions would allow to gain both currency and reputation with various groups and factions, which would allow the player to cause meaningful changes in the world depending on their decisions. A fantasy/fetish/kink unlockable skill tree would also allow for a sense of progression !

For what I don't want in the game... well feature-wise, not much. Unless an idea is too much trouble to develop or would hinder the player experience rather than adding to it, I'm open to everything. Content-wise there are a few things I know for sure I don't want in the game : highly illegal fetishes of course, watersports fetishes, gore fetishes, that kind of stuff. Other than that, I'd aim to have a fairly extensive and various amount of NSFW (and SFW) content to offer, so I'm good and open with everything else. And of course I welcome all ideas and suggestions.

I hope that gives a better idea ! I can go more in-depth again if you wish.