It isn't more interesting with solar panels because they won't generate nearly enough electricity in the winter. You should see both as entirely separate energy saving investments, not dependent on one another. (I'm however very happy with "free" cooling in summer)

You might need other radiators if your current radiators are very small. But you also might not in a recent house, or in a recently renovated house (e.g. the radiator are still sized on single-glazing-glass when having double glazing installed).

You can also choose in-foor heating with the next renovation, a lot of homes already have in-floor heating and it's very comfortable. You can probably also boost existing radiators with small fans on the bottom or choose an electronic back-up module which boost the temperature a bit on the coldest days.

Tldr: it really isn't that hard. The focus on hybrid systems in NL is purely thanks to a lobby from gas-boiler installers and manufacturers. Air/water heatpumps are a drop-in replacement in a lot of cases.