Maybe that's the trick - make the requirements for passing good enough that the minimum still requires learning and engagement, and then just grade on a straight pass/fail.

Basically, perhaps construct a class like this

1) HW 20% of the grade

2) Quiz (say 1 Q a week related to homework that was returned a week ago, give students a chance to figure out what they did wrong) - say 20% of grade

3) midterm and final, a 30/30 or 20/40 split.

one can adjust the percentages to achieve one's desired pedagogical goals.

personally, I don't find copying homework to be a problem if the student figures out what they copied. It's no worse than students frantically copying down everything the teacher puts on the board or slides which seems to be a common way students study.