Well, since they're revamping everything else, how about doing something that the player base would actually appreciate?
Right now, I cant tell you how many times a 10% upgrade has taken 40+ attempts, or a 5% taken close to a stack of preservation wards. And no, it isn't balanced by the number of times it goes below the expected attempts - that rarely happens.
How about a system where your chance of success increases as you make attempts? It doesn't necessarily have to be +10% per attempt for a 10% upgrade, but some amount to put a reasonable cap on tries. Maybe +4 or 5% per attempt?
For a 3% upgrade, perhaps +1% per attempt, and so on.
Instead of adding a percent chance after each attempt, just put a cap on the number of tries. So a 5%, could have a cap of 30 tries. A 3% could have a cap of 60, and so on.