Is there going to be account enviroments for developers to debug homebrew apps?

Pretendo does have plans to support third-party servers in the account server. I believe that this could be used by third-party developers like you who want to make and test new game servers. However, this is definitely a long-term plan that will take a while to get implemented.

In the meantime, if you want to self-host your own Pretendo server and develop on that, I made a project for that.