If you don't mind making a house rule, then sure. The "Wild" property for armor is kind of the same thing you're talking about, except with Armor. However, since all the player wants to do is apply his weapon properties to his wild shape attacks, I'd say that making it a +3 property is too steep... if it were me, I'd make it a flat 10,000 GP to apply that property to a weapon (based on the Transformative property). Alternatively, I'd make it available to the player as a feat.
However, I wouldn't just make the property/feat readily available to the player like any other feat or item... I'd have the player earn it through a personal side quest. You might not be into that sort of thing, and if you just want to do that, go for it... but in my games, if a player wants something very specific like this in the game that isn't in existence (but isn't unreasonable), my response is always "Yes, as long as you..." etc.
Let's take a level 8 druid for example who wants to do exactly what you're talking about. I might explain that the character knows about a sacred grove in the forest where a cult of druids know how to enchant items like that (or teach druids how to do it naturally, if the player wants to go the feat route). Then if the player takes the initiative to seek them out (with some skill checks to find the grove, of course), the druids may be willing to help the player if he/she convinces them to (with further skill checks), or maybe they just want the player to kill some critter nearby who has been "disturbing these woods". If the player helps them, THEN they will sell him/her the enchantment (for 10k GP) or make the feat available for the player to take.
This is just an example, of course, of how I like to handle house-ruled items/feats/etc. It makes the player work for what they want, it gives them a sense of accomplishment for it, it feels REAL in the game world instead of just some extra game mechanic, and it compensates for not normally existing in the game.