TL:DR: Resources presumably favor those who already find BG fun (aka - are already geared for pvp)
Assuming the box is enticing enough to bother, it WILL tank the economy - the demand will fall. If the costumes are not account-bound, their price will drop as well. Either way, the focus so far has been on external motivation aka turning BG into another farmspot.
Besides, people starting on the server are advised to focus on levelling/getting core eq first, which is sped up by focusing on PvE and ignoring PvP altogether. Althrough i suppose this isn't a suggestion aimed at them, it doesn't change the (implitcly too high) barrier of entry. Thus, my counterproposal is this: a 7-day PvP rental box, purchasable with bronze coins, containing whatever is consiedered starting PvP eq (beret, unfreezing armor, thara shield, etc?), that could be used only on pvp maps. A good addition to that would be the ability to rent specific objects from that box (still with bronze coins, but at a higher cost?), in case someone is halfway there.
The intended results are thus:
-offer the possibility for a quick dip into the pvp without getting stomped too hard
-provide a temptation to try PvP for more than BG coins (the best way to farm them is play bg durning the weekends, but then it would be a waste of the rental )
-a bronze coin sink for those who do farm at tamtam regions/do eden quests for badges
-the price of whatever would be in the box would drop - plausible solution: rental gear being actually weaker than the real deal
-people not liking pvp at all and being put off by it before making the investment, thus making pvp gear harder to liquidate - plausible solution(?) - answering and solving the why