Output audio to a different device from a plugin - is this even possible?

Please excuse my ignorance on this topic.

I want to make a plugin (AU, VST, etc) that is not standalone, and runs inside the DAW.
Let’s say there are 2 output devices, “Speaker 1” and “Speaker 2”, and that the DAW’s output device is set to “Speaker 1”. Would I be able to make a plugin that attaches to the master channel and takes the playing audio and outputs it to Speaker 2?

No you cannot do that.
Your plugin is inserted by the user on a track.
Your plugin knows nothing about routing: it just outputs buffers to the client (the track) when requested.
You cannot control where these buffers go.

Thank you!

That is just half of the truth. Technically you can open the a separate audio device from the plugin, but you shouldn’t.
The two audio threads will run on different threads and separate clock speeds, you might get drift, need to buffer everything…
It’s a nightmare and a bad user experience, because all routing should be set up by the host.