It is well known about a DTV dependent visa. The dependents get a DTV too. You stated an O visa as dependents on someone's DTV. I really do not think you are playing with the full deck. Stop consulting with the Leo and Chang.
I am pretty sure that Non-O Family visa is only available where the non-Thai has a Work Permit and the correct visa. Do you have a link stating where DTV family members can get a Non-O this way?
Foreign residents can as they are resident but need a long term visa. Tourists or UK visitors cannot. A letter of confirmation from a pal or relative says "Aye Greg is bunking here for a few days" is not going to work. :-)