Just my two cents here. I believe you may find less participation if you go with some of the changes you are thinking of. I am not participating myself for the contest rewards, in fact I split my first week reward among the three I featured. I joined because I think it might help someone new decide to stick it out while also benefiting me at finding connections of interest for me. 

But to come up with three new people searching areas that interest me takes hours. I read a lot of posts that are poorly put together or do not interest me despite liking the topic before finding three I feel comfortable submitting. I don't see myself having the time to curate subjects that hold zero interest for me, and would feel like a fake submitting posts that held no interest for me. 

As for gaining more interest, I am hopeful that those featured by us will see the value and decide to join in making this grow. I kind of hinted at this in my last submission hopeful that the new features would get it. 

Maybe you could add a bonus for theme while still allowing those like myself to submit posts not so tightly focused on a subject?