I sometimes have to add a new user (usually temporarily for support purposes) and it is always frustrating to enter in all of the details only to find Admin Tools says I cannot do it.
One solution would be to disable this feature via my IP address. A second solution would be to error upon the creation of a new user which would reduce the frustration. Both may be good options.
Just food for thought, it's your product, I would find this feature useful, but that's because I manage many sites.