Hi.
If the SAP Standard is only "adding" fields and not removing, renaming or otherwise modifying the fields I would revert to original, the additional fields should be not have a "Not Null" contstraint and will not cause any issues, the change in order should not cause an issue as a typical insert statement still provides the column name for the value as below and this is independent of the logical table structure in the underlying database which reorders the statement if it is differnet to the logical table structure.
In the case of a Z program which references the old columns and not the new ones, if they do not have a not null constraint they will simply be left Null (Empty). If you need definite confimation you should log an incident with SAP in BC-UPG component.
Thanks
Neil Ryan
SAP Active Global Support.
Example SQL Insert Statement
INSERT INTO Customers (CustomerName, ContactName, Address, City, PostalCode, Country)
VALUES ('Cardinal','Tom B. Erichsen','Skagen 21','Stavanger','4006','Norway');