Mines a early 4.0 with a touch of ally corrosion spotted around the extremities, It certainly isn't concourse and with 170,000 on the clock wears its scars with pride.

Now do I touch up and treat said corrosion which will involve painting of course or just sling some better panels on which might involve painting if I can't get the same colour.

Or let return to its natural state cos only ever gonna be a banger?

Treat it and touch it up !

If you have the time and the rust isn't deep it's pretty easy and inexpensive to do this yourself. Go for it!