It's definitely a conundrum. Either you curate rigorously, which can be read as gatekeeping, or you create one big bundle, which can jeopardise the intent. Hrm.

The first alternative idea that comes to mind is to coordinate an effort between multiple bundle-organisers, dividing up  the entrants; it's a sort of divide-and-conquer approach, which comes with its own set of problems (possible TOS issues,  possible gamer favouritism of one bundle over another...)

Another idea would be to consult the ratings to the games - and see how often they have been rated, and how well/with what intent. This would make curation more unforgiving, but it would ensure that the games you select really *are* the underdogs. Obviously that wouldn't avoid the problem of curation, even if it would be for reasons that are more in the spirit of it.

That's all the ideas I have.