In the solar physics community, there is a lot of interest in an out-of-the-ecliptic mission to observe the Sun’s polar regions. It would be especially useful for helioseismology, i.e. studying the Sun’s interior by measuring the vibration of the Sun, by measuring the Doppler shift of the surface. Helioseismology is a very powerful tool that lets us measure the rotation and flow deep inside the Sun, where all the solar activity originate. It’s powerful enough that we can even detect active regions on the far side of the Sun. But observations from the Earth are not very sensitive to what’s going on under the polar regions, which is crucial for understanding the 11-year solar cycle. A helioseismology instrument looking down on the Sun’s poles would solve this. It doesn’t even have to be directly above the pole - something like 45 degrees would do it, if I remember correctly.
But that’s still way more expensive than a typical solar observation satellite. It needs a flyby of another planet, or ion engines and lots of propellant and power, or a solar sail (which has never been successfully tested on an interplanetary spacecraft).