Warning: This mod is something I worked out for my own car (07 GT-B tbSTi SEDAN), using a manual for an 05 model and confirming wires myself with a multimeter. You can do this at your own risk, it is quite a simple mod but like all things you're best off understanding what you're actually doing. I didn't check the wagon version sorry, if you're handy with a test light it should be very similar so you can follow and work it out.
Purpose: This mod will allow you to operate your sunroof at any time. Instead of just when the key is turned to ign. This annoyed the hell out of me so I went about fixing it.
What: Basically you're just running a constant +12V power source to the sunroof instead of the current source which is on the ign circuit.
Materials: A length of wire, I used 8.75amp wire. Spade connectors OR soldering iron.
How: I haven't discussed removing panels to make access easier but it's all pretty obvious. Or ask in this thread if you have trouble.
Run a +12V wire to the cabin of your car directly from your battery (with an appropriate fuse in the engine bay). I went through the passenger side (a REAL pain) but it might be easier to just go straight through the drivers side, running the wire along the engine bay side of the firewall. Don't connect it to the battery yet.
I used a fuse block for my +12V source (I have 2 fuses in this circuit) as it'll be useful for other projects. This isn't required but it doesn't hurt. The larger red wire you can see goes through the firewall grommet, on the passenger side of the car directly to the battery (don't connect it yet). The thinner green wire, which was more than required but I've since forgotten the current draw is my power source for the sunroof.
I then ran the green wire behind the cubby which just pulls out, over to the fuse box area so I could get it up to the base of the A pillar on the driver side.
Now the fun bit. Remove the A pillar trim (from the top you need to pry it and release a metal clip with a long but slim screw driver) carefully as there's an airbag back there. Behind there you'll find this plug which has all the wiring for the electronics in your roof.
Disconnect this plug before doing anything else and bring the +12V source wire up to this area. In this plug there's a green w/yellow stripe wire which goes up to the roof. Separate this wire from the rest and cut it. Leave enough room either end to strip the wire a little and add connectors to the ends. If you put the plug back in now, your sunroof won't work so you know you cut the right wire (unless you cut a black one).
In my determination to make EVERYTHING I do to my car reversible I added a female spade connector to the end coming from the plug but you could simply tape this over instead. On the end going to the roof add a male connector as pictured (this wire isn't active once the plug is disconnected).
Now add another female connector to the end of your +12V source (which still shouldn't be connected to the battery) and connect this to the male connector running to the roof. Or solder it, whatever. Basically it should look something like this.
Tape everything up just in case. Reconnect the plug on the A pillar, connect the +12V wire to the battery.
Remove the key and enjoy using your sunroof. You may want to put the car back together too.
If you have any problems or questions I'm happy to help when I can.
Enjoy.