Hi Helen,
Thank you for sharing your question, and apologies for the delay! Currently there are no plans from Esri to incorporate CAD files into the Add Data Widget, however, we would certainly consider including this functionality if it were to be developed. Alternatively, a custom geoprocessing service could potentially offer this functionality, which could be plugged into LocalMaps. If this interests you, I recommend getting in touch with your account manager.
I hope that helps,
The LocalMaps Team