DH just ordered this piece (link below) for his office - except we got the book area at the bottom with a door on it (that is where he will file his papers.).

The center top section drops down... it has work surface and cubbies for stuff.

Maybe that could work???

Here is a link that might be useful: Harvey Ellis fall front desk

what about a "secretary" as inspiraiton?

The left section was display, but could be bookcase, or a combo of the two.

The right section had a desk area, w/ drop-down writing surface, and a compartment below, which could be a file drawer.

But there are others, like this one, that weren't divided in two vertically. This one has lots of shallow drawers but could have file drawers instead. And of course if GC is going to make it, it could be as deep as you needed, to accommodate files. And you might consider making it a bit taller; I know I always think those secretaries are a bit squatter than I'd personally like (though they often had a mirror, which was designed to be a face height for a woman.