As far as I remember, Quake 2 Lost Marine needs Doom3 v1.3, so in order to play it, you need to downgrade to that version. Ripping maps and monsters won't work because the mod needs source code changes which are in the DLL.
How to downgrade:
1. Download the 1.3 patch from here: http://www.the-emz.com/download/patch/D3_1_3.exe
2. Use Universal Extractor
to extract Doom3.exe from the patch, rename it to Doom13.exe and put it in the Doom3 folder.
3. Try to launch the mod with "Doom13.exe +set fs_game lostmarine". If it won't work, remove pak007.pk4 and pak008.pk4 from Doom3\base folder.