I tried it. Not bad for the size (of the model) and speed. Once you install all the massive number of libraries and things needed we are a far cry away from 25MB though. Cool project nonetheless.
To make the setup easier and add a few features people are asking for here (like GPU support and long text handling), I built a self-hosted server for this model: https://github.com/devnen/Kitten-TTS-Server
The goal was a setup that "just works" using a standard Python virtual environment to avoid dependency conflicts.
The setup is just the standard git clone, pip install in a venv, and python server.py.
ONNX runtime is a single library, with C#'s package being ~115MB compressed.
Not tiny, but usually only a few lines to actually run and only a single dependency.
Which is completely reasonable imho, but obviously comes with tradeoffs.
You would need to constrain the vocabulary to see any benefits, but that could be reasonable. For example, you an enumeration of numbers, units and metric names could handle dynamic time, temperature and other dashboard items.
For something more complex like offline navigation, you already need to store a map. You could store street names as tokens instead of text. Add a few turn commands, and you have offline spoken directions without on device pre-processing.