[rbanffy]

You'd probably need to pack a multi-mode propulsion system. Launch it so it can get a gravity assist from the Sun, deploy a solar sail after closest approach (or when safe) and ride the light pressure from the Sun to get as much delta-v as you can, then ditch the sail and fire up nuclear-powered electric thrusters for the rest of the trip. Dropping the solar sail part may be a good idea if its weight could be better used as propellant for the ion drive.

Then you have a hope of making the trip in a couple decades

[londons_explore]

Presumably when you get to the right distance, you'd want to circularise your orbit so you can use your new solar lens to look in many different directions.

Even more dV and time required to do that...

[rbanffy]

Yes... There will be a lot of braking involved, but we may start doing observations well before it reaches the intended circular orbit. I wonder how much such a mission would cost.