Your model is a little convoluted to simply move the "insert here" bar. What I am saying about the rounds applies even with your argument.
If the shell can successfully make the offset from the outer surface to the inner surface, no problem. But if the outer round has a smaller radius than the thickness of the shell, it will fail because it doesn't know how to "exclude" the round on the inside and hem the newly created unrounded seams.
Therefore, I agree that I would want to detail as many features as I can before the shell. In reality, within Creo, it just doesn't work well that way. The slots you have along the side edge, for instance, need to be modeled after the shell.
Best practice for shell is to lay out the basic shape; test the shell; add feature that may work with shell and test again. At some point you will realize the limitation.
As for making the part from a surface and providing an offset and ending up with an enclosed volume is a great way to do complex parts. I do not work on these often enough to make a habit either way. Personally I like working with solids from the beginning. It is easy to solidify surfaces into the solid for doing complex trims.
