A "one-man, two-vote" system of electing the assembly of a future independent Namibia (South-West Africa) is a feature of revised Western proposals presented yesterday to South Africa and to the political parties in the disputed territory, diplomatic sources said.

The Western consitutional plan envisages half the assembly being elected by proportional representation on a national level and the other half by a single-member constituency system. No provision is made for reserving seats on an ethnic basis, as urged by the white National Party in Namibia.

Envoys of the five Western powers seeking an internationally acceptable settlement in Namibia -- the United States, Britain, France, Canada and West Germany -- presented revised proposals to South African Foreign Minister Pik Botha in Cape Town. U.S. and British diplomats also submitted the new document to the internal parties in Windhoek, the Namibian capital.

The sources said they understood that the Western plan also was being given to the South West Africa People's Organization (SWAPO), the black African guerrilla movement fighting white rule in Namibia, and to the African states concerned.

After receiving the plan, Mr Botha told the South African Broadcasting Corporation that it differed on two important points from the original principles discussed by the Western group in October and November. These were the proposed electoral system and the dropping of a paragraph requiring that all private organizations be open to all population groups.