Adding an ad weight

I'm thinking about adding a weight to an ad within an ad group. The reason for this is that the client would like to have ad be displayed in a random order, but would like certain ads to appear more often than others. The way I think I could implement this is to add a weight field to the Simple Ad content type, and then modify the view sort criteria somehow to do a weighted random sort. I haven't worked through the details yet, but I'm curious if you can think this approach makes sense? I just started taking a look at the module, so I just want to make sure that I'm on the right track.

Thanks!