It is hard to define what "simple" means when you ask about a "simpler rendering engine". JSF is a very unique animal and I am afraid there isn't anything simpler that is also similar in the Java world.
My experience with JSF has been EXTREMELY positive, and this is coming from someone with years of experience developing under ASP.NET. The learning curve is still steep, and I can't imagine complex enterprise systems being possible without some form of custom Javascript and possibly even custom components, however in my opinion it is simpler than ASP.NET and much less heavy as well. They addressed a lot of the issues that made ASP.NET so difficult to work with, (Eg. simple client ids for the DOM, XHTML compliance).
I recently developed an application that will be going to production shortly using only Primefaces components, standard Mojarra facelets, one custom component, and a handful of Javascript/hidden input field workarounds for component framework bugs. It was stunningly easy aside from the few workarounds I needed to implement. I am extremely happy with the results, the stakeholders LOVE IT and I will absolutely use it again in my next project.
In formulating a team my real world experiences with it tell me that it is best to put a highly experienced web application developer as a lead on the project, someone with superb experience in Javascript, CSS and Java web technologies. The rest of team could be entry level developers with a modicum of guidance.