Idea for new draw scenario: If you can, in 1 move respond to checkmate WITH checkmate, the game is a draw.
Example: (and I don't know how to imbed a board in a post, so if anyone sees this and wants to either teach me or make this setup that'd be neat)
White king on h1, black king on h8 both sides g and h pawns on starting squares, white rook on b2, black rook on a7, white to play. Rb8 is mate, but with this change black can save a draw with Ra1.
I hear you asking "OP... why?" "because my inquisitive friend-" I'll answer. The basic "lore" of chess is two armies fighting to vanquish the opposing king, however if both kings on our hypothetical battlefield have a sword to their respective throats, I imagine they'd call it a draw. What do you think?
Technically the goal is to capture the king. With your rule, I could respond to your check with a check of my own, and you could choose to make a draw, or play on. Our kings are about to die, but if one dies the other will too.
Why would you want to add more draw conditions to chess?
Arguably it's too drawish as it is; that's why many varients reduce the drawing capabilites. (e.g. KoTH, any varient where you try to capture the king)