Hi Osiris,
Regarding your questions about 3D Characters, Plugin system... WME (not Lite) already has all those features and it's free, in fact you don't have to pay for using it.
WME Lite is intended to be a release compatible with all major OS (Windows, Mac, Linux...) and also with some handheld devices running iOS (IPhone, IPad...), that's why it implements just the 2D system so no 3D characters / Plugin system there.
As far as I know WME 2 will support 3D characters also in all major OS (Windows/Mac) as its graphics layer is based on a 3D library that already support those systems.
If you want to develop a game that runs just on Windows, go ahead with WME as it supports all the features, but if you want to create a game running on several platforms, use WME lite.
Regards,
Manuel Martos