Changing the Sequential Numbering profile value

We are on 11.5.10.CU2.  We implemented document sequencing this week for AP.  I chose the "Partially Used" option fo rthe Sequential Numbering because it seemed like it would be less problematic.  Now I find out that ERS invoices do not get a sequence assignment when the setting is "Partially Used".   It sounds like we have to change it to "Always" to get the ERS invoices voucher numbers.  If so, won't this create problems now since some invoices were already created without sequences?