A parcel of Stirling Ridge in Yarralumla would be given over for diplomatic estates but the ''vast majority'' secured as open space under proposals released by the National Capital Authority.
Stirling Ridge also would no longer be considered for a future prime ministerial residence ''due to areas of ecological conservation value'', and Attunga Point, west of the Canberra yacht club on Lake Burley Griffin, instead favoured as a future site for The Lodge.
In another of the proposals released on Friday, Yarramundi Reach grasslands on the northern shore of the lake would be protected from future development.
The authority also suggests removing all reference from the National Capital Plan to a possible pedestrian bridge across Lake Burley Griffin after the Immigration Bridge proposal was scrapped.
The authority has sought public comment on three draft amendments to the National Capital Plan. Draft Amendment 78 sought to adjust land boundaries in Yarralumla to accommodate diplomatic land use, secure Stirling Ridge as open space and foster management of Attunga Point as a possible future location for the prime ministerial residence.
Authority chief executive Gary Rake said about seven diplomatic missions could be built on the south-west side of Stirling Ridge. He said that area was not environmentally sensitive. By contrast, land ''on top of the ridge should not be developed for any use''.
The Stirling Ridge site covers 41 hectares, and three hectares would be required for the diplomatic estate. The result of the amendment would be to change the majority of Stirling Ridge from land set aside for national capital use to open space in recognition of high conservation values.
While there were no plans for a new Lodge, the site on Attunga Point ''provided an opportunity to develop a new official residence in a prestigious location similar to that of the Governor-General's residence''.
Should the building go ahead in the future, a realignment of Alexandrina Drive would be required.
Mr Rake said most of Stirling Ridge would be protected, including the walking track around the ridge and the endangered button wrinklewort wildflower habitat.
The authority also put forward Draft Amendment 80, which would assist in protecting the natural and cultural heritage values of Yarramundi Reach by removing the assumption the land was reserved for the future use of the National Museum of Australia.
Yarramundi Reach is a large undeveloped parcel of national land on the shores of Lake Burley Griffin near Scrivener Dam that had been identified as the preferred site for the National Museum of Australia by the National Capital Development Commission in the early 1980s.
Now that a museum was located on the Acton Peninsula, the amendment removed the requirement for the needs of the museum to be taken into account when managing Yarramundi Ridge.
Draft Amendment 79 removed reference to a pedestrian bridge connecting the Acton Peninsula to Lennox Gardens, Yarralumla, across the West Basin of Lake Burley Griffin following Immigration Bridge Australia's decision to use an alternate site in the Parliamentary Triangle for commemorative purposes.
If another pedestrian bridge was suggested in the future, the proponents would have to start afresh with the approvals process, Mr Rake said.
The amendments are open for public comment until December 14.
Mr Rake said the authority was also likely to be questioned about the proposals when it appeared before Parliament's joint standing committee on the national capital during the consultation period.