"Promoting unseen content" won't be solved by increasing the size of the front page because the amount of traffic and attention a post receives is directly proportional to the absolute ranking (anedotally, posts from my blog which hit the Top 5 got 3-5x the concurrent traffic than posts at the bottom of the front page).
Adding more entries to the front page won't help at all.
Adding more entries to the front page won't help at all.