yachiyo: In one game I play, they have a weekly challenge that basically has 3 random gameplay(suvival contest, most kill contest, mission completion contest) and each week the challenge will start choosing a random mode...

Note: the features of the challenges aren't being updated weekly, just during special events, there are special new features... Otherwise, the challenges basically just keeps repeating weekly...

The rewards aren't that great but some are still useful...and in about 3 months of playing, you can get something useful out of all the rewards you horded..

Regarding alts...we can just report alt abusers so they can't abuse rewards..

Hope you introduce something like this to BD someday...maybe not now, but some day