Now that Mt. Gox no longer offers MTG USD redeemable codes, what other exchanges offer these vouchers / redeemable codes / coupons?
Not exactly whay you are looking for, but might satisfy your use case.
LocalBitcoins.com is offering coupon functionality where LocalBitcoins.com users can issue their own coupons. Coupons are paper coupons which the users can print themselves and then sell e.g. in net cafe for cash. Bitcoins are substracted from the issuer walet when the coupon is redeemed. The coupon model is based on Easy Wallet functionality which you may be already familiar with.
Example coupon below:
The functionality is currently available for limited audience on LocalBitcoins.com site.