This can be done in 2 ways either through a BLTH or a Policy Xpress Policy:
Write a BLTH java class to replace accented characters. Invoke a BLTH on handleValidationBeforeSubmission or handleValidation. It will allow the user to do the replacement before task is submitted and access the replaced string in PX as well.
Find some sample BLTH java class under IM tools folder.
Policy Xpress Policy:
In the Policy Xpress Policy, under Data -> Category: General -> Type:String Parser -> Function: Replace All
Suppose Original String is: Alãnã
Have "Sub-String to be Replaced": ã
"Replace with": a
So the new value should output as "Alana"
This can be done for various other accents that is desired.