I did it old school and created a shortcut with the following target path:
“C:\Program Files (x86)\Steam\steamapps\common\Homeworld\HomeworldRM\Bin\Release\HomeworldRM.exe” -mpbeta -overrideBigFile
Place your ship hod into an appropriately named folder under Data > Ship
Make sure you have a .events and .ship file with a matching name. Just grab one of the other ships .event and .ship files and in the .ship file, comment out all the weapon and engine lines near the bottom.
Edit your startingfleets.lua under Scripts > Startingfleets to add your new test ship to the skirmish start fleet.
Also if you want to post the hod, I’ll toss it ingame real quick.