Online publication system for a journal
In addition to the OpenJournalSystems (OJS) software, I'm aware of the following free and open source solutions that you might want to consider. They are similar to OJS in terms of functionality, but, perhaps, simpler:


DPubS (Digital Publishing System);
EPrints.


While I would strongly prefer open source software, just for completeness, below I will mention some commercial hosted solutions:


Atypon's Literatum;
bepress' Digital Commons.


Finally, a few words on alternative solutions that you consider. In my opinion, the CMS solution is feasible, but, you will likely to lose some features found in specialized open source solutions, such as DPubS or EPrints, for example, document workflow, flexible user rights management and more. I would be very cautious about and, actually, don't recommend the handmade MySQL/PHP system (or any other handmade solution, for that matter) due to various reasons, including, but not limited to, significant efforts required for creation and maintenance of such system.