I've messed with Python but I'm not a programmer or developer. There are probably software EMULATORS that can emulate specific hardware such as the ICs used in the venerable RA-800. AI large-language models can write code, and might also easily translate existing code from one language to another.

Roland already has the source code. An app having the core chord recognition and pattern transposition logic, using MIDI and a minimalist interface shouldn't be difficult or expensive.

The potential market for mobile device apps is MUCH larger than the market for hardware keyboards; sales would recover the translation costs in a short time. The real risk is that a successful app backed by one of the "big three" might cannibalize sales of hardware arrangers. And Roland specifically hasn't made one of those in over 10 years!