How to set up required privileges to use PL/SQL APIs in custom schema

Hi All,
I'm using a custom schema for connecting via JDBC and calling several APIs (like FND_WEB_SEC.Validate_Login, EGO_ITEM_PUB.Process_Item, ENG_ECO_PUB.Process_ECO, BOM_BO_PUB.Process_BOM) with this user. As APPS schema is like superuser for EBS, I decided to connect to a custom schema instead. But as it turned out to be very difficult to set up all required privileges for mentioned APIs and I would have to provide a general method to do this at customers, I'm no longer sure if this is the right approach. Besides, FND_WEB_SEC.Validate_Login is not valid for non APPS accounts as described in