Streaming levels and updating dynamically at random or statically


How can I replace a level that is being streamed to players?

For example levels 1,2 &3 are all streaming. I want to replace level 3 with level 4 so it now forms part of the streaming levels.

What are important ‘nodes’ for C++?
Are there drawbacks to this?

On a longshot :

Can I add these levels to an array of blueprints and change them at random?
What function can I use to blend in the changes to make the streams less abrupt?

Thank you very much,