Yup. If you look at the Nokia N97, it wouldn't be too hard to move the D-pad to between the red and green buttons on the face (you'd need to make the diagonal button less diagonal, though). Which, IMO, is where it belongs :-)

You could use a dpad the size of the ones on the E61i or E71, as well. In fact, if you directly stole the ones from the E61i, you'd be able to put it in the same side-rail space that's on the N810, and you'd have a 5way dpad PLUS 8 other buttons (IMO: menu, escape, home, zoom in, zoom out, full screen toggle, and then maybe two soft buttons). Or you could use fewer buttons and make it more elegant. But, my point is, you can easily put a smaller dpad on there, and Nokia already has those smaller dpads in their parts inventory.

(or, the E71's button group, which then also incorporates the throbbing status light into the space between the dpad ring and select button)