Can I get the German National Visa application submitted in a German consulate in a country and get the passport stamped after visa approval in another German consulate/VFS in another country?
If I answer your question in a generic way i.e. specifying if it is possible or not then: yes, it is possible to do that. A number of applicants get their visas stamped in another country. Having said that the process could be troublesome and the embassy/consulate concerned would take it on a case basis.
However, it is totally at the discretion of the embassy or consulate you are dealing with and the answers you find here are mostly opinions and would be case specific. As suggested in the comments, you should call up the embassies and try to explain your situation.