An approach I've seen before is to find a length of the correct grain vinyl (that matches the door panels). You can often find it at a local fabric store in black or white - colours can be an issue.

Using 3M spray adhesive and a heat gun, attach the vinyl to the degraded door panel, using the heat to help stretch and conform the vinyl to the curves.

For the leading edge at the door, there will be the issue of thickness to consider - it's possible to shave down the backing of the vinyl a bit and wrap it over.

For the footwell lights, leave small flaps of material that can be tucked into the slats and fastened behind.

For the upper area where the boot attaches, there's no great way of hiding it other than

a) try to thin down the vinyl and attach the catwhisker over it

b) be neat with your edges on the other parts, then the convertible top boot will cover up the work.

The groove in the middle of the panel will not be quite as crisp/defined, but the vinyl will follow enough of the contour to look decent. Far better than a ratty old panel.

'Cudas are a less forgiving because the grooves aren't as deep and there are two of them. Though adding the woodgrain can help to mask this issue....