I vote for NOT putting the Plug-ins into Main Calibre as it will limit PI repair to the release cycle (waiting a week is H*ll
)
OTOH
If it is only the
Distribution of the PI that is included with a normal release, then relocating (and maybe applying a visual 'style' to the label that indicates a normal part of Calibre) makes manual, Mid-Release (of Calibre) PI upgrades available.