[SF-Junky]

... and by 'completely' I mean invisible to sensors and eyes. I want an object that can not be seen by the eye, can be targeted if friendly, not be targeted if hostile (can easily be solved by using the 'stealth' flag) and that can move at lets say 50 or so mps at maximum.
So a bit like those nav points from WCS, just able to move. ;-)

I already tried to just remove all the textures from a retail Ulysses fighter, but this doesn't work.

[Droid803]

Use the texture 'invisible' ?

[Killer Whale]

FRED, make object invisible? I think there's something like that.

[Mobius]

Use the texture 'invisible' ?

[Nuke]

then use stealth then set to neutral

[Herra Tohtori]

Switch to transparent textures via texture replacement.

Thrusters... either give it invisible thrusters or no thruster textures at all, or turn the engines off when it's invisible (disable engines temporarily or something).