You could setup a web Template (no need of COTG in this project unless you want it to run on tablet, phone, etc…).
Once you form is loaded up on the Web you could use Ajax call, to a Workflow process, that would return you the data from your DB. Then you would use that data to fill-up your list in your Web form. Upon submit, the selection of the user would be returned to Workflow for you do handle it.