The Team and I have been discussing for the past week possible solutions for players that have too many items to be handled by mere boosting. We were looking for a solution that will be fast to implement and will give an adequate solution to the group of players affected. Just to give you a general idea of the size of the group; there are less than 2000 players with 1K items or more.
We went over several ideas (including the ones you posted here on the forums) and we have decided to give players the ability to convert items of specific tiers to PowerKits. This solution will allow you to easily handle big numbers of items - instead of manually selecting thousands - while still reserving the power value of each (+a small bonus).
It will work by you first choosing tiers you want to convert (Common, Rare, Epic etc). The system will then calculate the overall power value of all the legacy items you have in that tier, and will replace these items with a few power kits that will have the same power value + some extra % bonus. So hundreds of items could be converted to 3-4 (or more) powerful power kits.
This system also allows you some control. For example, you can choose not to convert the legacy mythical items and use only a few of them as boosting material while keeping others in your inventory.
Please note this system transfer the responsibility of handling the inventory space to you. If you won't convert items to power kits by the end of the grace period, you will still have an over-the-limit inventory and will not be able to open new boxes from you unclaimed boxes section. While I can't yet say when will we have this conversion option rolled out, we will, of course, make sure you will have enough time (probably around 7 days) to use it while in grace period. And yes, we will extend the grace period if needed to allow you to have that time.
Feel free to post below if you have any questions on the process or need any additional clarification.