Hello David,
Thank you for taking the time to consider this.
I would like it even more if I can control which plugins they see and can use (even if the plugin would be functional to them). this would also cover the issue of "this would not work for all plugins"
Why not just list all plugins in the Reseller center / Privileges (Edit reseller privileges & nameservers) and allow us to choose which ones each reseller can see? Even the option "Show plugins" (on / Off) would be an improvement.
This would also be the most relevant place to add this in my opinion, as it already lists all the other WHM components.