Hello Wolfgrin,
I've made large campaigns for NWN2, so I am not too bad a writer either.
For now, as I started to do it, you can modify the file that contains the dialogs. You just need a text editor such as Notepad++ (use language/javascript option so you can check the delimiters).
Here is what I have done up to now. I have modified some dialogs : Sal and a large part of Garcia. NPCs and RPCs, but no seller yet. The idea is to increase immersion, give characters some breadth and put some more humor. (At least I hope)
File modified : C:\Program Files (x86)\Steam\SteamApps\common\Jagged Alliance Flashback\game_Data\StreamingAssets\Original\Localization\US\US-dialogs.json
You can find the modified file here :
http://1drv.ms/10SWeh6
The folder contains the modified JSON file and a sample snapshot.
Though you can reacquire the original file through Steam, make a backup first, then replace US-dialogs.json by the new one.
You can switch original and modified file at anytime (exit the game before of course).
As Glettkin said, we'll have to wait and coordinate with Shanga for more ambitious projects