Hello Andres
It's a very common practice to open a customizing transaction frequently changed on a productive system, so that you don't need to generate a request for each change.
I wrote the following documen which explains this procedure for the PP transactions:
Open a customizing transaction for changes on the productive system
Since I'm not an FI consultant, I cannot tell exactly what it the impact of this change, however, since it has been asked by your functional consultant, I don't think that there is any problem. In fact, your FI consultant is the most appropriate person to judge if this change is necessary or not.
Besides that, since there is a note explaining how to do that, I think that it's a common practice.
Regards
Caetano