heres how you do it -
backup the file called Default loadout (to keep for online play)
this file is found in the SFC 3\assets\specs folder
after making a backup copy for switching the file, do the following :
Right click on DefaultLoadOut.txt and select properties
take the check mark out of read only
Click OK
Open DefaultLoadOut.txt with notepad
click on Format and turn off word wrap
click on Edit at the top and select find
type in Romulan-Battleship
in the line of Romulan Battleship you will see the entry like this
Romulan Romulan-Battleship Scimitar scimitar NS R-TRACTOR-V:3 R-TRANSPORTER-V:1 R-ARMOR-V:2 R-COMPUTER-V:1 R-CLOAK-I:2 R-THRUSTER-V:3 R-SHIELD-X:1 R-SHIELD-X:2 R-SHIELD-X:3 R-SHIELD-X:4 OFFICER:ENGINEER: OFFICER:SECURITY: OFFICER:HELM: OFFICER:OPS: OFFICER:TACTICAL: OFFICER:MEDICAL: R-WARP-SB:1 R-DISRUPTOR IIIF:8 R-DISRUPTOR IIIF:6 R-DISRUPTOR IIIF:4 R-DISRUPTOR IIIF:2 R-DISRUPTOR IIIF:1 R-DISRUPTOR IIIF:3 R-DISRUPTOR IIIF:5 R-DISRUPTOR IIIF:7 R-DISRUPTOR IIIF:10 R-DISRUPTOR IIIF:9 HEAVY PLASMA TORPEDO:13 HEAVY PLASMA TORPEDO:15 MEDIUM PLASMA TORPEDO:14 MEDIUM PLASMA TORPEDO:12 LIGHT PLASMA TORPEDO:17 LIGHT PLASMA TORPEDO:16 LIGHT PLASMA TORPEDO:19 LIGHT PLASMA TORPEDO:18 R-IMPULSE-V:2
find NS and erase it..
save the file
now the Scimitar is selectable in single player campaign mode of he game.
That should work because it worked for me, and now the Romulans are more powerful than ever...