Just had one of those "hey, wait a minute..." idea's
Back in the days i did a lot of flightsimming you could download templates you could use to create your own aircraft skins. To see how an idea i had will look on a model i looked em up again. Found this site with all kinds of military fonts and markings you could use for printing custom decals with your own printer. You just need to resize to fit your model and voilá
Please bear in mind that inkjet printers do not print white though but you can buy white decal paper for those occasions.
http://www.simmerspaintshop.com/forums/downloads.php?do=cat&id=3
Somebody else probably thought of this waaaay before i did, but just in case...
Richard