Yes. I do something similar on my site. I would investigate using Custom Capabilities for your modules. However, I have a lot of custom PHP managing user access, and if you don’t know much about coding, I’m not sure where the best place to point you would be for examples.
If I understand correctly, you want something that is only available to level 3 members and not level 4 unless they buy it separately?
If I were in your situation, I would instead have whatever “level 3” people purchase to be actually be purchasing one or more custom capabilities. Doing it this way would then keep users separate and you wouldn’t have to try to tinker with the system (since by default, everyone with lvl 4 access will also have level 0-3 access too).
I don’t remember where the Custom Capabilities section is in my admin, but that is the feature I would look for and research implementing.
Hope this helps.