Probably not possible, without lots and lots of reprogramming. Game Extracter and MexCom use completely different engines. MexCom uses MexScripts, which are sort of like Basic for archive formats, while GE uses plugins that are compiled Java scripts (not to be confused with JavaScript).
Hmm... perhaps that could be a worthwhile project... If mexCom could be 'trained' to support GE plugins, that would add support for at least another 150+ formats... I'm not sure who here would care to undertake a task like that, though... Mr.Mouse and Rahly are probably still cringing from the work on Rahly's Plugin Manager.