Markus, to be honest, I will have no effect wether is part of the included Libs or not with Pythonista. I can just ask. Many people ask via the Pythonista forum for third party Libs to be added. https://forum.omz-software.com/category/5/pythonista
Currently Pythonista version 2.0 supports Python 2.7. Version 3.0 has just started beta testing a week or so ago.
But regardless if Tinydb is included as part of the dist, anyone can still do a pip install as I did. Of course, if it's included sharing code gets a lot easier.
But as far as performance warnings go, I think you cover it in your docs. You are quite clear about its limitations. Hey, it's dicts. But it still seems very fast. SQLite also has its own warnings about usage/performance etc. I haven't done that much yet, but I think in the Pythonista environment can be very handy. Keeping in mind with Pythonista, he also has a XCode template which can prepare Pythonista projects for apps to be sold on Apples App Store. I have never done this, so I really don't know how involved it is.
Not sure how much work it would be, but have you thought of doing a wrapper/database connection to SQLite? No more functionality than TinyDb supports now. I am sure it's not trivial, but would keep your initial idea alive, I think.
But I think no matter how you cut it. SQL is painful. If you are into interfaces, games or whatever, data storage/retrieval can be a real pain if databases are not your thing. Let's face it for a simple game, you don't need much, saved states , high scores etc. they still need to be saved and retrieved, searched etc. even that simple stuff in SQLite can be a headache. Then people start using things like ConfigParser way beyond there limits or intended purposes.
So I guess what I am trying to say, personally I think there is a place for a lib like Tinydb. And its performance weakness is also it's biggest strengths. Just working with dicts and list of dicts.
But I will do more testing... I have read through the docs. I will have to read more I am sure.
But Markus, I am still a newbie. I was a professional c programmer many years ago. I am learning Python as a hobby. But I still have apps in mind to write for my friends. Like restaurant menu apps, (small) hotel booking system. I can see how Tinydb would be great for these projects. And even if not all the data aspects, still a lot of it.