In that case, you can do one of two things. You can edit the tactistype.ini and change the initial weapon configuration of certain shiptypes so that you'd always have that weapon (be sure not no remove in the fleet loadout panel).
For that you'll have to modify:
styp_t_Angelwing, styp_ep6_AngelwingM, styp_ep5_AngelwingM,styp_ep4_AngelwingM,styp_ep3_Angelwing, styp_ep2_m3_Angelwing, styp_ep2_Angelwing, cls_Angelwing and/or styp_ST_Stiletto_corvette.
Or:
You can open the files episode_x.rules 1 through 6 and in each mission add your device to the stock of usable devices, by use of the function "uAddDevicesToStock(device, # number of available devices in stock);" if you're unclear as to where to put this, just add it with the rest whenever they appear.