gimp 2.2.12 multilingual does not start up if configured in this non-default directory structure.
Directory with GIMPPortable.exe (PortableApps, for instance) +\Apps\ +\GIMPPortable\ +\GIMP\ +\gtk\ +\Data\ +\GIMPPortable\ +\settings\
Following GIMPPortableSource\readme.txt this configuration should work. I get an obviously incomplete information message saying: 'was not found. Please check your configuration'
There's a bug in the current release with the old split directory structure introduced in the Beta 1 of the Suite (as opposed to the new internal App/Data split). This structure will either be fixed or dropped in the 2.2.13 release.
Side note - I'm debating dropping all alternate directory structures to simplify the code. You'll still be able to use any you'd like with an INI file.
Sometimes, the impossible can become possible, if you're awesome!
I agree, today you have really too many alternate directory structures. A lot of extra work for you to maintenance all of them. Anyway my favorite would be a structure that easily allows to separate all user data from all application binaries.