Wow I hope you can succeed, having a converter like that would make things very convenient. MS3D is a very simple editor to use and it's convenient to create simple objects quickly. It's currently a problem exporting with animation weights, which was my motivation for trying to make the conversion.
Some thoughts about DBO Format:
The MS3D code is definitely really rough, zero polish. The priority at the time was just get it working. I never got back to tending to it. It was part of a larger project where an MS3D file could be converted to and from DBO, just without the weights and animations. The DBO file format specification is rather vague in areas, and I was constantly getting some of the bytes wrong. Especially with the weights. However the huge hurdle came down to rotational values, converting from Euler XYZ to Quaternion. In the end I figured it out, it took really long time, but I was too spent to tackle the last mountain which was encoding the animation at the end of the DBO. The angle conversions are just the first step, in that process since you need to make sure all bones have correct initial rotational values. Not to mention new angles in animation frames.
Plus good grief the non animation section of DBO it was a mess of convoluted parent frames, sibling frames, child frames, empty frames. In MS3D format they just list the bones, list the rotations, etc. So simple. In DBO its so vague it's all a big tree of frames, and half of them don't seem to do anything. Like all of the mesh data was packed in the parent frame, and there's even a list of all of the bones in there somewhere. There are Matrices all over the place, with empty of default data sets, no explanation why they are needed just that they have to be there.