You can use the auto-install GW 1.1a version with JSGME. During installation of GW 1.1a just change the installation path and direct it to JSGME's mod folder.
IIRC you may have to create a "header" folder (i.e GW 1.1a) as I think the installer will only create the data folder. The file structure in JSGME should be as follows...GW 1.1a/data/....
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