With many of GOG's games getting non-English versions after the fact, I hope that you will be able to pull this off for TIE Fighter as well!

I'd especially be interested in the German version, of course. Other than X-Wing, TIE Fighter didn't get a localized voice over (the German CD-Rom Edition still had English voices), but got all texts translated.

Also, does GOG accept scans of the (localized) manuals etc. to add to the downloads? I would offer to scan my stuff.

The Floppy Disk version of Tie Fighter was dubbed in German. And I think there was a German Add-On for the Floppy Disk version of X-Wing as well.
While we are at it, I'm willing to offer the XWINGCD manuals in German as PDF.

Do you have "Die Akte Farlander" with your CD-Rom version? It was missing from mine... obviously they were out of print when the game was still being IN print.

Unfortunately, I don't have "The Farlander Papers" in German. On the other hand, I'm not sure if it was included on the CD-ROM Edition.
I also don't have "The Stele Chronicles" and TIE Fighter's manual and reference card in German. We probably lost them while moving.

The German reference card and manual of X-Wing are included as PDF on the German 2001 re-release of the CD-ROM Edition (the one inside the DVD-case with the original Floppy Disk cover), which I also have.

Well, I have everything both games came with (in German) and still in brand new condition. Also right now I'm betting on the German "Farlander Papers" on eBay, and once I get those, I'll start scanning everything at high quality.

Have you been able to get "The Farlander Papers" in German on eBay?

That's great news. Well done. :)