Is there an easy way to put the character that is in the glyph when it’s empty in the Caption? (‘Postscript name’ maybe)
Yes. Start a new font. This uses the WGL4.TTF template, which contains images of all the glyphs, and all the mappings and postscript names. Just copy the glyphs that you need to the font you are working on. Instead of just pasting the glyphs, use Paste Special and check the boxes to copy postscript names and mappings (and over-ride existing mappings if you wish to do that).
Accents are best added by using composites. From what Erwin says in this post, I think you will soon see a feature to automatically complete composites from the mappings, so scripting probably won’t be necessary. All that one will need to do is make fine adjustments to the position of diacritics, which one would have to do after using a scripting language anyway.