daily mission suggestion

hey, here I am once again with a little suggestion

I think it would be cool to allow players to purchase ONE letter each month for like 10,000 GP/1000ZP, but they can't let them build up.
after the month is up then the chance for buying one letter that month would be expired if you didnt already do so. just like you have the awards for how many missions you do per month and once the month is up they reset. (heart grenade, shotty, etc)

because I'm sure there are a ton of players who are stuck trying to get that one letter and it would be their choice whether they want to spend the money on a letter when they have all but one.

a good way to take advantage of that would be buying a letter on the 30/31 and the 1st. but then you would have to wait a whole month to buy one again even though it may not take that long to finish getting all the letters.

O_O