Foxpup, did you manage to make it not crash but without it all working? See, the furthest I got was, I managed to have Blue Shift listed in the Custom Games list, the menu, loading and console backgrounds work but after selecting "new game" or "hazard course" the maps don't load but it doesn't crash either. I think it doesn't crash because I edited the liblist.gam file to the appropriate version of my Blue Shift game. Not sure.
Anyway, what if I created a new mod (like copied the sierra/Half-Life/gearbox folder) and added all the Blue Shift content to said folder. Apart from the PAK and WAD files what else would I need to replace?