I've filed #23094 a while ago asking to be able to pack extra deployment descriptors (that should be closed, by the way). but the new dialog in #2026 is overly complicated.
Asking for a name, description and "default path" (what's that supposed to mean, by the way) is just too much just to add an extra file to the build. I would suggest that this should be changed the following way:
ejb-jar.xml and web.xml continue to be special deployment descriptors, managed by IDEA, and of course mandatory for the respective types of modules. An application server plugin may add more mandotory descriptors. The user should be able to add extra descriptors, which are just files that should go into META-INF or WEB-INF when idea builds the module. No name, descriptior or default path for these files, just a simple, plain file list.