It took a bit longer than I planned, but here it is – all the data from HKJC of horses and races since 1979 (except for one horse from 1977!):
It is a web frontend (called datasette) to an SQLite backend, so you can run SQL queries against the data. You can also download the data as CSV or JSON, or the SQLite database itself from https://hkjc.guru/hkjc.db
I plan to add more premium features as time goes on. Please send me any feature requests or questions.