Instead of continuing work on my class diagram, I started to look into the more typical work of setting up the infrastructure that the web app portion of WESS demands: users, roles, configs, ORMs, etc..
I should definitely revisit my drafting board. I thought of setting up some sequence diagrams, maybe use case diagrams for the install/login/administration aspect of it. Even these parts need to have a plan reflected before work can really begin. There's a lot here to chew on, and a good balance of actual software construction, user interface design and UML planning needs to be found.
It may be beneficial to write many plugins for different parts of my application, to keep things organized via the plugin manager for mojolicious. I should keep this in mind when writing the class diagrams.
I also looked into how the routing and rendering systems works in mojolicious. I'll continue to use the embedded perl. I'll also definitely be taking serious advantage of CSS and JS, which will force the use of more modern browsers, but is worth the trade-off.
