Oh, it is in effect kinda similar. Though it does it through gearing

https://en.wikipedia.org/wiki/Hybrid_Synergy_Drive

Not quite motor->battery->wheels. I guess to have the generator be removeable you need a much smaller engine as well

I think the Chevy Volt is what you're talking about. You plug it in to charge and when the battery runs out, the engine runs to charge the battery so you can drive until the gasoline runs out. The engine isn't connected to the wheels at all. It only charges the battery as you drive.

I didn't realize it was that separated. Would be cool if you could detach the engine entirely and leave it at home when you don't need it. Or buy the car without an engine and rent one when you want to do the annual roadtrip

AIUI the Hybrid Synergy Drive combines aspects of a series and parallel hybrid, for efficiency at both high and low speeds. I think this is the main reason that pure series hybrids are not more popular.