No, no, no, I am getting old! Agreeance is not a word!
This innovation has nothing to recommend it. It's not shorter, it's not clearer, it's not anything but wrong. The word is 'agreement', dammit.
Mind you I never understood that other abomination, 'admittance'. This could often be seen written ('No Admittance') in gold paint on wooden doors in past decades. Nobody ever spoke the word though, which had a calming effect on me I suppose.
NEED A PEDANT?
PETER THE PROOFER COULD TEACH THE QUEEN THE QUEEN'S ENGLISH!