Xur should sell every exotic including armor and weapons but for 40 coins each for Christmas Or he could price the exotics. For example gjallarhorn maybe be 200 coins or ice breaker 180 coins as a new system. Price format the exotics so players can see steady progress toward what they want instead of selling an exotic once and never selling it again to keep it rare. This way they can still be rare and may have to pass up on other exotics they want at most it may take players weeks or months to get that many coins and even if they do they have less exotics and not staking them