With FFTPatcher 0.493 (the latest version that has released recently) you can change what formation sprite the unit is linked to in the Jobs tab of the FFTP underneath the Equipment checkboxes. Check out what the normal values are for things that are known for examples (IE regular Delita has 3 and 3 next to Formation Sprites in FFTP because his is the 03 entry in Unit and Wldface. Holy Knight Delita is 0 and 78 because he doesn't normally have a Unit entry, but 78 is his correct Wldface portrait. You can just overwrite something unused). Then you just need to change the matching formation sprites in Shishi (found in Other Images under Unit and Wldface).