Well, I saw an interesting post on the Forums lately.
Something that should be done. Make the same thing with the 4 slotted purchased vehicles through ARMAS. They appear to buy on contacts in case you delet'em. But with the weapons no. Yeah, it happens to accidentaly delete a weapon when distracted.
So it's possible to make buyable on the contacts the weapon you bought on armas with an Unlock Item in the mail.