I just finished my BSc/BCom (Maths & Finance) degree last year. If you want challenging and interesting problems, you can do pure Maths (like extensions of Discrete Maths). Also, if you pick it up quick enough, there is certainly less work and study than Actuarial.
The main problem is that Maths & Finance doesn't lead to any job in particular. Those jobs that are in maths and finance field, eg derivatives trading, quantitative analyst, etc, usually just require smart quantitative people (eg engineers, actuaries, physicists, etc) as the finance can be learnt on the job.
I think if you can beat or are on par with the top people in the quantitative area, ie, students doing actuarial, maths, from the Sydney unis, then you stand a chance. Otherwise, it's not clear what doing this degree will lead to.