I agree, Lara, partial credit for short answer questions is perfect for math. I already try to predict all the ways students can input an answer to see if they are the right track, but being able to assign different point values to different answers would be awesome! AND if the a specific answer can have an automatic feedback response (from the teacher) that is specific to that answer, that would be amazing!!
As far as bonus points, maybe offer a ‘star’ icon that teachers can select so that the points are not added on, but students know that they really rocked that question and went above and beyond the expectation. Later, the teacher could tally the stars and award bonus points in their grade books.