As of right now I'm using bare Python, just outputting to text using print statements. I've successfully emulated Quest's general structure of rooms with objects in them, an inventory and so on. It's a lot of different Classes, but I have a framework down right now. Currently you can walk around a few test rooms, interact with and/or pick up objects in the rooms, talk to an NPC, and I have methods running every turn for the usual stuff, like accidents, thirst, hunger, and potty stats. You can use items in your inventory, too, and equip certain items. Basically, I have core functionality down right now. A new system I'm using is called the Sammi System in-game (Yes this is a reference to Sunny Paws). It uses an item called the Sammi Watch to track your uses of the potty and your accidents and attach them to a virtual potty chart, and you can be demoted or promoted through potty training ranks based on your chart. Your rank determines what kind of underwear you can wear, and other characters can see your rank. I think this is a good way to not immediately punish accidents with a demotion to diapers or pullups while still having the eventual threat be a demotion. Also, it lets me use the ranks and the potty chart in unique ways, like having a character try and hack your chart, or something. It's another thing to play with, and it fills the same role as the Sammy Plush did in Sunny Paws, in a lot of ways. The watch even has flavor text for certain actions. Other than that stuff, there isn't much set in stone. The game takes place in a massive "Daycare" filled with people who don't know how they got there, and those people play various roles. Some act as helpers or caretakers, while others are in a similar situation to you. I think that this kind of setting lets a lot of interesting ideas thrive, which is why I'm keeping some things vague. Anything ABDL related could probably happen in a setting like this, which is the point. The "Daycare" is big, and more of a massive maze with various places to explore, people to meet, and items to get. Honestly, let your mind go wild with ideas. As long as they can translate to some kind of gameplay concept, like changing your stats or giving a debuff or something, it's effectively on the table. Even if it's just an item in the world with flavor text that's more content added. If you need any more specifics just ask, I'm probably forgetting to mention something important.
Also, Python really is a godsend for this project. I know Java and a bit of C#, too, but I feel like either of those would have been a nightmare to work with in comparison, especially because of how many resources there are for simple Python problems, and how often solutions to problems are just an import away. I'm not even going to touch on JavaScript. Whenever I release the project I hope that people mod it like they did Sunny Paws, because my Class structure for making new Rooms and stuff is, in my opinion, pretty easy to get a grip on. Basically, without getting too technical, every object, for example a Rattle in your inventory or a Kitchen room, is its own Class which is the child of some generic Class. This lets me add more complex functionality to specific items while repeating as little code as possible. It's a lot like making an item in Quest, except without all the messing with the UI, which is what turned me off of it in the first place. I love the "genre" of games that Quest allows you to make, it's just that the engine itself is weird, complicated, and slow, and the editor glitches a lot.