Selecting journal reviewers through cover letter I was planning to use mdpi.com to submit a paper to "Entropy" journal. The journal perfectly matches the area that my paper covers. However, they require a cover letter to five reviewers selected by myself:

http://www.mdpi.com/journal/entropy/instructions


  Coverletter: Check in your cover letter whether you supplied at least 5 referees. Check if the English corrections are done before submission.


Is this the standard procedure? Can you propose other similar journal? I am getting afraid that receiving feedback is not an easy task, and I can wander with the paper for a year or so.
They don't require you to send a cover letter to five referees, but just to indicate in your cover letter the names and contact info of 5 potential reviewers. It's just to help them finding reviewers for your paper (as they say, they might not use those you provided). But I don't think you need to contact the reviewers first. 

As far as I know, it's a pretty common procedure, I've seen it for several other journals.