Welcome to Glest, Seto. I think you'll find Glest to be very modable and very fun to use.
To answer your question, there is no current neutral option, nor any way to change the "alignment" of players mid-game, though there's no reason to believe that won't ever appear in the future (alliances was a popular feature request once). However, at the moment, GAE and MegaGlest are planning a merger into one, unified engine, so feature requests are partially on hold at the moment, and priorities will probably be redefined.
I look forward to seeing some mods from you. I recommend you take a look at the
Glest Guide (currently undergoing a major revamp) and the
Glest Wiki.
