Hi,
I will suggest that you could copy and paste the exsiting project, and open it in SSDT then delete all the unwanted objects, e.g. roles, measures, etc., leaving the tables and datasources for further usage.
Theorathicaly, you could copy the .bim file of the existing project, open it with Notepad or other editor, delete thoses too. You get a new .bim file and you could start the job on the new project.
Considering creating new datasource and tables are also easy in Tabular project, why not just create all the tables directly in new project?
Regards,
Lukas