I honestly can't see you making more money by going exclusive anywhere. It may have worked out for some, but I don't think a 50% increase in royalties can be offset by a 4/5/6 times drop in the number of agencies you submit to. If you want to simplify the process then I'd consider submitting to BlackBox. While it's not something I'd normally recommend for a number of reasons, if your goal is to make things simpler then that could be the way to go. 15% loss in your royalties, but just one upload required, and they do hit Level 5 on Shutterstock in the first week of the year... which is nice.