At first it sounds like it would change the game substancially... but if you think about it, it's not all that frecuent to be able to mate your oponent next move when you're about to get checkmated yourself.
If the point of this new rule was to "equalize" the game for black and somehow make up for the first turn advantage.. then I'd say it doesn't achieve that. It looks to me more as a new draw rule that only aplies to black. Something like "let's make the perpetual check rule only count for black".
It really wouldn't do anything about white's initiative as the starter, since the white player (if played accurately) will allways be the one with 1 extra tempo. This rule would try to "catch up" this extra tempo at the very end; but the whole outcome of the game is already influenced by the different timing.
I might have messed it up.. I hope you can understand my point.
Cheers!
First off, thanks for all the replies!
Now I just want to ask: If white has the first move advantage, shouldn't a rule be changed in one and ONLY ONE regard, namely:
If white checkmates black, but on the very same turn black can do the same (checkmate white), shouldn't the game be drawn???
This situation is only for black,only for black, not white, in other words: Black just checkmated white but white can checkmate black on his upcoming turn. In that case the game is won by black, since it was white who moved first...
So what do you all think?