By adding new racial trait for all races, except 1 race, I think.
IE, Trait: General Race Ship Construction.
Then add this trait as second tech req for all designs except those that you want to have access with your race:
Name                          := Escort
...
Number of Tech Req            := 2
Tech Area Req 1               := Ship Construction
Tech Level Req 1              := 1
Tech Area Req 2               := General Race Ship Construction
Tech Level Req 2              := 1
...
but
Name                          := Cruiser
...
Number of Tech Req            := 1
Tech Area Req 1               := Ship Construction
Tech Level Req 1              := 5
...
Then edit AI_general files for all races (except the one with limited ship access) to add this new trait and make new EMPs.
Edit: huh, typing too slowly and refreshing page too rarely   
 [ May 14, 2004, 21:05: Message edited by: aiken ]
 
 [ May 14, 2004, 21:05: Message edited by: aiken ]