You can map additional entities on the same tables for the purposes where you don't need the excessive amount of fields.
LLBLGen Pro supports table splitting, i.e. you can map more entities on the same table, which all have a 1:1 relationship with each other, and where they all have a subset of the fields (plus PK field).
It's likely you don't need all the fields ever. So you have table Customer, and you map 'Customer' on that table with the PK and 10 fields, then 'SpecialCustomer' also to that table, with 1:1 relationship with Customer over PK and you add additional fields of the table to SpecialCustomer. 'Customer' is the PK side of the 1:1 so inserting goes OK. It's of course required the fields not in 'Customer' are all nullable in the DB otherwise inserting a Customer will fail.