Custom code

Just a thought. I have my own layer between the presentation layer and the nopCommerce original business rules layer. That works great for me since its not so sensitive for updates

But is it possible to have an extra layer that is incorporated in nopCommere (whit all the references and so on) where you could easily implement your own code. That layer should be updated very carefully.
This way it would be very easy to share code with other people. Let’s say someone writes a function that copies categories. Then it would be easy to implement this. Perhaps the person that implemented it could send out a .cs to be inserted in your own code.
And how about having a “tools” menu on all pages that calls one class so it’s easy to insert functions.  For example “Copy”, “Renum”, “Delete all”.

Is the plugin model (global event handlers) not sufficient? You create a DLL, add references to the Nop Business Logic DLL and other DLLs as needed, write your event handlers, and attach them in global.asax. Nice seperation of concerns but you're running in Nop's context!

My original suggestion

Thread on the actual implementation - EventContext