Suggestion for a better and new keyboard shortcut

There are certain actions in elementary OS that doesn't have a keyboard shortcut assigned to them out-of-the-box. One example is closing application. It doesn't have a shortcut to it even though it's very useful to have one. I've assigned super+x to it, IMHO I think it should be implemented out of the box and be listed in the keyboard shortcut help window. I think it's a good addition and will be welcomed by new users.

Another think is that certain action uses keyboard shortcut that might not be ergonomic. One instance is multitasking view which uses super+down. It's intuitive because of how multitasking view in elementary OS is designed but it requires 2 hands to execute because how keyboards are designed. In my opinion, it'd be better if it uses super+ whatever key is next to the cmd key, like super+a or super+v for view.