You think
I think I to work on the right lines.
The registration have 3 side.
User side - registration request, verification code typing , activation validation.
Tech side - simple mail checking, (or improved email checking), pre-reg activate time-out
Admin side - monitoring/ban/delete, or only admin can register like now
You say: user starting a registration, wait for approved by admin, and finish the reg process if he get it.
My idea not to horn in user or tech side.
If anybody want to join, then can register, go through the full (simple or multistep) registration procedure. Like now.
He to obtain a user status instantly, can login and enjoy the forum. It's userfrendly
But he know too it's limited status and need wait for full approved.
At the time admin/gmod can approve her account. Or Disapprove. But alone at this moment because haven't unnecessary todo with fals reg - this adminfrendly
And this method possible easy switch to the free registration too.
But this my personal equation.
Mail to admin question. A big forum have more admin/gmod. Who get this mail?
I think best, if waiting users or number of this users showed to all admin/gmod in forum.