Is there a way to allow for clients to run commands with hubnet?
I see a tag in a button, for example, which can send a message, but can the client dedicate some computational power?
No. The regular HubNet client doesn't do that; it's a thin client only.
It is possible to write your own custom HubNet client, that does anything you want; the server doesn't know the difference as long as the client sends the right messages. But you'd need to build such a client yourself. There's a repository on this theme at https://github.com/NetLogo/HubNetClients , but I see it hasn't been updated since 2011, so it might need tweaking to be usable in 2016.