Bosch Heat Pump + Hydronic Coil?
Heat pump + hydronics is a fantastic combo, provided you can get an air handler that supports it

While you are correct that the combination of a heat pump with hydronic backup heat is uncommon, it is not bad by any stretch of the imagination -- when an efficient boiler is used, it will beat a forced-air "dual fuel" setup any day of the week when it comes to overall fuel efficiency as the hydronic setup can run the hydronic coil at part load to make up what the heat pump can't provide, something a forced-air furnace can't do, and is far easier on your house's infrastructure (and the electric grid!) than all-electric setups are, especially in cold-climate areas.

However, due to this rarity, not all heat pump manufacturers provide air handlers that have hydronic coils factory fitted in place of the normal electric standby heat.  I am not certain if Bosch provides that option; if not, you will need a skilled HVAC shop's assistance to field-fabricate or field-modify an air handler for your setup.

You probably want a water tank somewhere in your setup though

However, on the hot-water side of the picture, you probably do not want the boiler to try to serve hot water loads directly -- this is inefficient as it forces the boiler to try to balance between competing needs.  Instead, the superior approach is to use an indirect tank hot water heater that runs as a hydronic zone off the boiler, with the water in the tank is heated from the boiler water via an internal heat exchanger.

A high-efficiency boiler and indirect tank is as efficient as a good gas water heater, while providing excellent longevity with the availability of stainless steel or cement-lined tanks (vs the normal glass-lined steel tank) and superior capacity due to the extra heat exchanger area compared to most gas water heater designs.  It also avoids the comfort issues that are possible in tankless setups (such as the "cold water sandwich" problem), and requires less peak capacity from the gas service.