Depends what chapter you are in:
If you are still in Ch 2 or 3, getting Viconia in your party will drop your rep by 2 points. If you kick her out it will raise back up 2 points. So if you get her, you can do two more quests without upsetting Korgan or Edwin. After that you will have to be tricky. If you kick her out right before you get a reputation bonus, your Rep will shoot up to 20. Since that is the max, the game will not give you any more, so when you take her back into the party, it will drop back down to 18. The only problem is keeping Ed & K far enough away, that they don't leave before you have finished all the transactions.
If you are in Ch 5 or greater, you can become the slayer to drop 2 points whenever you wish. Just don't stay in that form too long or you will die.
Resistance to Tyrants is Service to God.