To use cockpit mod with other ships than retail you must create your own *-shp.tbm file and put these lines:
$Name: the name of the ship to add cockpit to (must be the same as in the tbl/tbm where the original ship is located)
$Cockpit POF file: the name of the cockpit.pof file (i don't remember so you'll have to take a look inside the cockpit.vp file)
Also for blue planet look at the bpcore.vp file for bp-shp.tbm to find the ship names
then you tbm file should be in yourmod/data/tables to be of any use
I wanted to do it for my personal use but I prefer without cockpit after testing it, so it's probably not worth it.