Hi Mark,
There is no reason other than to appear on the list of photometry tools someone in the VSS needs to be successfully using it for photometry and submitting observations to the BAA online database. With a few tweaks to the AAVSO file format you can upload those files.
The reason for not adding more tools to the list and approaching developers is time. Running the photometry and spectroscopy databases are voluntary roles, so the list of tools is based on what members are using. I am happy to offer help and advice to anyone wishing to submit observations to the database.
Best wishes,
Andy
British Astronomical Association
Supporting amateur astronomers since 1890