I don't have all the details and I wouldn't be allowed to share everything anyway but if I remember correctly, it has to do with different shop systems between the 'old' version and the version currently on the GF Client.
Store is a separate web application that can only be run in a primitive browser inside client.
Again - since the mechanism for receiving rewards is ready, there are absolutely no contraindications to resetting the reward list.
You have a ready, safe mechanism, already implemented in luncher, and this is only element (with emphasis on safe) that would require some work - but it is already ready.
Mechanism "just" resetting reward list takes 5-10 minutes of work for a beginner programmer (it doesn't even have to be a programmer, just someone who manages the server and has access to CRONTAB, MySQL/SQL (or another database engine on which server emulator runs)).
I have been building data management systems and creating online stores for over 10 years.
But when I read the reasons you give, I rub my eyes in disbelief - that a multi-million-dollar company has such primitive problems (assuming, of course, that you(GF) have no attitude "don't give a damn" to Aion Live anymore).