Why change the home page layout? Is there are particular reason you would want to do that? For the most part, anyone wanting to have a link from you would consider the look of the home page a secondary issue. It's the DA they will be looking at with the added bonus of a boost in traffic while it's on the home page if they write a great headline and have a great image. Be careful about how you go about 'advertising' that you accept guest posts and if you are going to start publishing more posts, perhaps ramp it up steadily instead of sudden splurges.