An OXP that allows the player to choose among the base skins and those available in all of the installed OXPs for the same ship. You pay a small fee and presto: your scratched and bruised bird looks like a shiny angel of death, to match the fearless commander inside.
I do not know if it is possible to examine the other OXPs to find available skins. I recall that ships may be customized in stats and equipment as well, but I hope that will not interfere and that a customized cobra is still a cobra in terms of dimensions.
For good measure, the creator of this OXP may include as many pieces of spaceship artistry as he or she can get his hands on

Ideally, there would also be an easy way to load additional textures, but I suppose these need to conform to pretty exact proportions..
The same could also be done for missions: at one point you must disguise you ship as someone else's, including a transponder code and also the paint job. Nice for infiltration, but the you have to go home and convince your friends that the paint job is a fake...
best wishes,
Oscar