[Pro Sites] Issue with subsites we have not part of Pro Sites Levels

I have a number of subsites not assigned to a Pro Sites Level. These are sites for custom one-off clients that are on separate, custom plans.

Unfortunately it looks like Pro Sites implementation of Premium Plugins does not account for this scenario. So not sure if this is an issue, a feature request or simply need some sort of a workaround.

Basically what is happening now is that if I assign a plugin to a specific Pro Sites Level, my custom clients will see that plugin fine if activated. If not active, even though I want to make it available to them, they will see the [Level] Only upgrade message. This would happen also if I have activated a plugin for them and they decide to de-activate the plugin for some temporary reason, like testing. They will not be able to activate that plugin again and that would be a big issue.

Maybe I need to have the option for a level to not have specific pricing and not display in the shopping page matrix. Then I can name that level something like Custom and assign that level to my custom clients. I can position it in the hierarchy to be at a higher level than my most expensive tier, so it would list all the plugins from that tier, in addition to any plugins I want assigned to only that Custom level.

I also would not expect my mass market clients, with specific Pro Site (regular) Levels to be able to see the Custom Level plugins listed in the Plugins page.

Makes sense? Maybe as simple as being able to add levels that do not have pricing assigned; then those levels would simply not display on the upgrade/shop page AND not have those respective plugins appear on plugins pages of other Level users?

Or is there some workaround to achieve this?