Hello there. 

 About the cloaking effect: Great! 

 If a ship can use this should be triggered by an entry in the ships.tbl like this:
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$cloakdevice   YES
   +cloaklimit   YES
;; if the ship cloaks only for limited time
      +cloaktime   50
;; max time ship is cloaked in seconds
      +cloakreload   20
;; cloaking device reload time in seconds
   +cloakfireprim   YES
;; if ship can fire primaries while cloaked
   +cloakfiresec   YES
;; if ship can fire secondaries while cloaked
//   +cloakfiretert   YES
;; if ship can fire tertiaries while cloaked
//only if tertiary weapons are added
   +cloakshields   10
;; percentage of normal shields that works while cloaked
(might be above 100 ?)
   +recloaktime   0.1
;; in seconds
   +recloaksound   cloak.wav
;; obvious
   +recloakeffect   recloak.pcx
;; effect for recloaking
   +decloaktime   0.2
;; in seconds
   +decloaksound   decloak.wav
;; obvious
   +decloakeffect   decloak.pcx
;; effect for decloaking
   +cloakedeffect   cloaked.pcx
;; effect for being cloaked
   +cloakedsound   cloaked.wav
;; sound if cloaked ship passes near the player
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I think it should be possible to be cloaked for unlimited time (like in WC or Star Trek) and there should also be the possibility to use different effects for activating, deactivating cloak and being cloaked. This way you could for example add a ship to your mod that's completely invisible while cloaked (simple black texture only needed as far as I understood how this works). 
 As for tertiary weapons I think they should be real special weapons like the shockwave of the Homeworld:Cataclysm Dreadnought or the main beam of the B5 Excalibur that drains so much energy that the ship is effectively disabled for a minute after firing it. 
