HomePod and Siri on external device

Can I use the HomePod like any basic “dumb” external speaker to simply channel commands to and audio from an iPhone, essentially using the iPhone’s Siri to handle all those things that the HomePod cannot do natively? E.g., I can tell Siri directly on the iPhone to use a dedicated radio station app to stream that station. Can I set it up so that the request goes to the iPhone via Bluetooth and then plays via the HomePod. Even better—could I switch back and forth so that, e.g., I could make a call using the HomePod?