Power BI Token Request 256 character limit

I am dealing with an issue where I need to exceed the 256 character limit for the username() field in Power BI while generating an embed token. We have a list of accounts we need to pass in to filter the Data Set. Some Users have around 400 accounts which could total near 2000 characters. We do have Account Groups Ids that would work for most customers by passing in the single Account Group Id. However, some customers need a longer account string that exceeds the 256 char limit. Does anyone have any work-arounds or fixes for exceeding the 256 char limit on the username() field?