I guarantee you you will hate at least one of those core courses. I heard that not many people like MGMT1001. Arts people do well in that course, where there is strict referencing. Do something else, like a free elective.
Hmmmm i cant think of any other comp sci related courses. I didnt do ENGG1000, but many people said it is a wam booster if you work hard on it. You can do physics, but its way different from the hsc and its mostly a wam killer. You can also do the other sciences as well.
By the way, if you...
Oh no no no... it is pretty hard to get a HD in Arts. Most likely you might get a low end Distinction if you work your ass off. There is a lot of competition in Arts, since the ceiling of difficulty isn't very high.
I think it is just next to impossible to finish double degrees in 3 years. Unless you want to study more in the summer. Commerce courses in the summer involve paying your own fees.