Ahh okay.
From a preliminary once-over, /wps/FILES and /wps/WPSLIST look interesting. Obviously all the wps/theme-name.x.y.z.wps files are display-specific versions of the WPSes.
It looks like WPSLIST's <wps></wps> stanza is going to generate a theme .cfg file for you. Looks like the <rwps></rwps> stanzas are for remote control LCD themes, so you probably don't need to worry about that. If your theme uses a font not included in the default build, you'll need to copy it into /fonts/.
I don't have a build environment on this PC (I couldn't say I'd really be bothered testing anyway), and pretty much all of this I just guessed from looking at the source structure on SVN ... but that seems like it should do it.
EDIT: I probably should have read the header on WPSLIST first as it confirms some of what I just said...
Also, mods... what is the point of allowing BBcode and HTML? It's just annoying when my angle brackets disappear.