You don't really need more than a 32-bit unique integer column and a GEOMETRY to register a
table with ArcSDE. When I use SQL to create databases, I use SQL, with only a few registers
at the end. I mostly use the ArcSDE API to load the data, but only because I've got a very
powerful ASCII loader -- there's no reason SQL can't be used for that as well (provided you
validate your geometries to be sure they honor ArcSDE topology rules -- lines vs. simple lines,
polygon boundaries which are non-intersecting,...). There is no inherent geodatabase complexity
when working with "simple feature classes", you just don't get the full monty in terms of object
behaviors, complex topology, et. al.
- V