Due to my workload and a busy weekend, it will be sometime next week before I fix the one I have posted.
I have so far a working DXF-DWG, DWG-DXF, and DWG-DWG (change the version) on the Multi-file Batch Convertor using ODBX, I plan to add DGN, SAT, PDF, and maybe more, but those aren't exposed to ODBX AFAIK, but I am not going to use Express Tools.
Thanks for the inspiration and help to get back on this.
Besides the original DGN batch convertor I found and adapted, I was surprised nobody ever tried to make an improved version before.