In the hit calculation routine, at 08028C18, there’s the command to branch to 0x8028C3C. This does an inventory scan and has a hard coded check for item id number 8A, meaning the binding thing from the seal to the hit bonus is its item number. Changing its effect is likely difficult(unless you can asm)
… Just leaving this here for documentation.
To change which item slot is the emblem seal, you’ll see at 0281B2 is
8A 28. Simply change that to
XX 28 for the emblem seal as item ID XX. Or, 00 from no emblem seal.