You could custom shape some from foam paneling or wood just cut some shapes of what ya think would look nice then keep them lable them where they went so you can duplicate take a piece of Masonite from the depot. Use the old door panels for a template. Trace the old on a peice of paper then make up a design you like then use those shape you made to make it 3d or make extras then you can pop it in the can and see how you like it if the arm rest would be comfy to rest arm on. Then when this is done you'll need some plastic sheeting some spray adhesive preferably masking tape some body filler fiberglass resin and body filler spreaders. And maybe some alluminum foil. If you want the panels all fiberglass then you won't need the Masonite. But you'll need a template to use under the glass if you use something like cardboard wrap tightly in plastic and tape securely. Then you'll want some fiberglass resin coat it with some resin then if your wife has some old nylons use those on it they stretch Nicely and done absorb so much resin as fleece does coat it Nicely i use usually these tools a few chip brushes a shurline touch up pad non foam Back get one with the red handle and a few reloads as you'll need them as well as some paint tray liners. Forgot to mention those at first. After your done doing a layer off fiberpanties ha ha had to say it sorry, the do another two. After they are hardened use a sharp knife and cut off the stray edges. Then pull off the nylons off the templet should go nicely as they don't stick. Then place panel in the car you can see you're panels getting closer. You now can use your shaped pieces you've made that will help contour your door panel. Now you can choose to make those out of harder plywood which some people like or cardboard. Remember you'll want duplicates.!! Then it's nice if you trace your shape to your panel as a reference. You'll then want to use your pieces and attach then to the panel tapes your friend or if you use plywood use finish nails or a pin nailer to attach them. Once this steps complete I usually like to do this to the other side as well to catch up. Then if you used plywood i would sand the rough edges down to keep the bumps to a minimal. Next step some people like to use great stuff to form the panels other use actual foam ment for this which I know you can get from tcpglobal.com the products closed cell foam this is similar to great stuff wear styrene gloves this will keep foam from getting on hands if it does or the resin does you can use nail polish remover acetone or xylene to get it off. Laquer thinners not the best but ok to use. What you'll do is be sparse on the panel you as foam expands a lot  spray inbetween the gaps of the shapes you attached on the panel then once it's done and dried you can trim and shape the panel to your liking. Another thing you could do is find a arm rest from the junk yard and attach to the panel and build off it. But after your foams done can use the glass and go over the foam and shape your panel. Another way instead of the foam if you want all glass is do all steps up untill that and then  make a top to the shapes and form it and then use the plastic with the spray adhesive and an then use glass over it then once hardend i would do a couple more layers and then remove and you'll have your top portion. I would then remove shapes had do a few more layers on the bottom. And then you want probably 36 g and a orbital sander or had sand and get the high rough areas down. Then you'll need to use a scrap 1by or smaller to go around the top peice then use a nail and attach the wood. Then once that's done use another few nails attach top to bottom piece. Once this is done put panel in car you can really tell now if you like it or not. If you do make sure clearance isn't an issue. Proceed to next step.  you can mix your filler. Use approximately 1" ribbon hardner to golf ball filler. Mix well . Then apply smoothly and neatly not vigorously. When the filler is done hardening you can now fill over it and see if you can fill any low areas. If you can you can mix a lil filler up and go over them usually you want to over lap low areas few inches on each side preferably. This will liminate doing over. Then when filler is done you can sand if would do 80 g and then 180 you could use some rustoleum bombs from Home Depot to prime it I like the regular non auto primer.. You can decide now if you want to have panel upholstered. Or painted. Or if you wanted you could have top section upholstered and bottom painted up to you. This maybe something to look into on the panels for your car. Not to hard once you get going I've done this several times to other cars and trucks

Ya I couldn't sleep ha ha I needed something to make me sleep and thinking about cars does that ha ha. You could look up how to make a fiberglass sub box which aren't good do to rattle but should give you some stuff to go from on how to make your door panels. I did same type of deal to make a third brake light panel. And now while I'm doing other stuff on my ride I'm going to make either a custom fiberglass or a ply wood trunk enclosure for my car. I'll look similar to this