The Regent will mostly say that if they were somehow able to summon the entity in their immediate presence, they would be able to do something about it, and this is what would be most useful to them. As it is, there is no way that any of them would be powerful enough to counter it directly, were it to fully manifest... though, they also believe that it would be less likely to do so now that it's no longer Inoseri.

The Regent will have a big laugh, first and foremost, and then say no. Does Ciel truly believe that their name is 'The Regent'? What would such a signature even mean...? If they truly want to be rewarded for their performance, they should be brought to the Regent's presence afterward. That can be their 'reward'.