I get the standardized control scheme, and I think its a great idea. But what about the 2nd player? Are there suggested/standardized controls for the second player? 

This is my suggestion for the second player.

D-Pad -> WASD

Enter -> Left shift button

A -> L button

B -> K button

If you have any better ideas, feel free to use them. 

Yeah sorry we should have standardized them a bit more beforehand. Hopefully I can get some input from devs this time and we can find a better default layout for default.

I would probably do WASD vs Arrow keys, though not sure about A and B. I guess A and B could stay as space/alt for player one, player two could maybe have 0 and . on the keypad? Though not everyone has a keypad. Maybe ctrl/shift for arrow keys?

Another keypad option is 8/4/6/2, and maybe 0 and . for A and B.

Your best bet it to probably support multiple layouts, or even input configuration.

Just a reminder that WASD excludes countries that adopted other layouts (like AZERTY in France, Belgium). Sure QWERTY is the most used layout, but please allow other layouts to play by switching WASD to ESDF or, even better, add an option to redefine keys (which imo is part of the polish ;)