The only alternatives to full skin replacement have their drawbacks. If you weld patches in, there are no feature lines to strengthen that long panel. You could flange the roof and plug weld a patch and use heat gel (works very well) but you're still running the risk of warpage and oilcanning. You could also use a metal bonding adhesive like 3M 8115 but then you could get "ghosting" which shows the outline of the patch when it gets hot. Pretty good chance of that since it is a roof and is a horizontal panel. I'll jump on the "replace it" bandwagon on this one.