It depends how far you want to go. If corrosion still isn't a problem then get a length of steel. Heat gun any seam sealer or underseal off the area, then flap disk,wire wheel it all clean to metal then rust treatment then weld the new metal on.
But I replaced my panels properly. I can't really see a beneficial reason for quickly knocking something up. I know you weren't scared of getting the welder out. But with a 8mm spot weld drill bit and 1mm cutting disk you can remove the front arch and then the front inner cill and spot weld new ones in then loads of sealer. Could you maybe fabricate something to bolt to the chassis that covers the areas you want to protect?


