haven't done it before but I wouldn't expect any serious problems mashing tiles with shept jsp/tagx. I would start from this tiles example and merge with the default shept form. Don't get confused by the different taglib notations you can use either this (snippet)
or the other
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
BTW - would you mind sharing an anonymized subset of your data model with the public ?
I believe that its pretty straight forward to set up a full featured application and also a great excercise to learn spring basics with shept but maybe I just suffer from tunnel vision. Note that shept is no big-deal framework - it's overall size is at best 1-2% of springs overall size. If you like we'd set up a public repo covering a few entities and forms on github and jointly develop a frontend using shept in the next couple of days.