Barn find mx5

I'd agree with the last few points. It's all very well concentrating on the welding first but, if it's stored outside, there's little point in tackling the rust until you fix the source of the problem. These things rust from the inside out, so the insides of your replacement panels are going to rust up in no time at all if it's still leaking into the inner structure.

I would get a replacement rain rail and a drain brush, makes sure any water than runs down the hood is exiting out of the vehicle rather than in it. The drain tubes have a little rubber flap (poor excuse for a valve) in the bottom at the exit from the inner sills. This often gets stuck causing a blockage, or debris gets stuck at the restriction. This causes a build up of rain water in the tube which leaks out at the join into the inner sill. Or as quite often happens someone gets too zealous with the brush and disconnects the pipe from its connection inside the sill/quarter. Then get a cover or half cover to give a first line of defence that you're not going to be precious about. I wouldn't think about replacing the hood until the dirty side of the bodywork is done. Just my 2 pence.

Also check the ribs on the sills either side of the jacking points, they should be drain holes but often get squashed or gunked up and need to be cleared/opened with a screwdriver. Not unheard of to have closed holes and sloshing water in the sills as you drive.