Moon Tester Tool can be used by a monkey to install an extension if its only issue is that it doesn't target Pale Moon. In either case, all extensions come in a form of .xpi file (basically ZIP archive) which contains text install.rdf file, containing basic information about the extension such as GUID, name, version, which applications it targets etc. The Moon Tester Tool basically rewrites the file so the extension targets Pale Moon.
Information about the max version of the target application is ignored unless strict compatibility checking directive is present/enabled. Some extensions contain the directive that the XPI content should be extracted upon installation, for these extensions you should find the original XPI file.
AFAIK, New Moon still accepts extensions targeting Firefox, so if some extension doesn't work, parts of its logic may have to be rewritten to accommodate for changes in the browser core.
I supposed you'd have to find the old documentation for XUL coding and info regarding whatever MCP folks changed that broke the extension to be able to fix, the developer tools baked in the browser may also give hints.
I modified Destroy The Web some time ago to remove dependency on deprecated FUEL, which is long gone from Basilisk and will eventually disappear from Pale Moon as well.