Ability to Decrypt PII info based on Logged-in User

Many clients has Data Encryoted using their application logic and that data is imported into OneLake.
Clients are looking for ability to decrypt the data only fly based on logged-in user (RLS/CLS). 
Since these values are encrypted using custom logic by app, we need to decrypt them using custom logic as well.
This is an ask from many-many customers.  Same time being able to read key from Keyvault is also very much needed.