Following are the custom solutions:
1.) Remove the config from NACE for mail subject line. In your custom program write the logic for mail subject line. In code logic you can prepare subject line as you want.
OR
2.) I will not suggest this but if you want to continue with your NACE config then this will be one of the approach. There are few fields in EKKO table of CHAR length 25 and more. If any of this field you think not important from business prospective for your client then you can write a code logic (In any exit or BADI ) to put creator name in that field. Then directly use this field in config. But do all the impact analysis prior to doing this. 
Cheers,
Prakash