Unfortunately, since OBSE isn't a replacement .exe, you can't just rename it. The OBSE.exe calls Oblivion.exe to run, so if Oblivion.exe isn't what it expects, it will give you the error (and it obviously would be a different .exe than expected as it is the OBSE.exe with a different name). So if editing the config file for Galaxy doesn't work, I don't know what to tell you. I also had the same problem with Arx Fatalis and the Arx Liberatis mod. I eventually had to concede that it wasn't going to happen.
The_Pastmaster: I've tried a lot of things: Changing file names, editing file paths, editing Oblivion_default.ini, editing the goggame-1458058109.info but nothing I do works. It's like Galaxy is actively circumventing my changes and it's getting annoying.
Anyone able to assist? :)
EDIT: Did you ensure that Galaxy was completely exited when you made the edits to the info files?