The system as it stands isn’t too bad - though probably half the rewards are useless or lame. The pick three mechanic is nice (especially since most of the options are crap, it’s nice to pick the one that is most needed).
Two changes I would like to see:
(1). An alternate mission for the raise a skill three levels. Most of the time I have nothing to level up, so when that is the case either don’t make it appear, or give me something else to do instead, something that I can do and without forcing me to spend gems. Missions that require gems to be spent are lame and suck.
(2). Allow the rewards at the end to be collected ANY time and not just on Monday. Also, once they are collected, start a new bar filling up! Casual players still get the rewards about weekly, but die hards might be able to get the, slightly more often (which solves the issues others are complaining about on filling the bar too easily or no motovation to do all missions).
And a bonus third thing: when the bar is full, put out a red dot and draw attention to it, so people know it is full and collect their reward. (Also, once full, more missions completed should go towards filling the next bar and not just be lost if it wasn’t collected yet.)