To send two solar probes , the nearest possible of the Sun and shoot stereoscopic pictures of the surface. In visible light , UV , X rays. And get superior imaging of sun spots , granules , and so on.

If relativity is to be believed ; Mass curve space and light rays. So the Sun must act like a giant refractor. i propose send a space ship far away from the sun where is its focal "point" and make incredible pictures (Or go back tail down)

To send a Michelson interfometer in space and do mesurements in earth orbit and farther and farther.

On earth , during a sun eclipse , to do again the Eddington experiments with a team of good amateur astronomers.And do it again.

And many other i could perfectly do myself ....