NTS will be told to appoint a new board of trustees to replace its existing 90-strong ruling council as part of a drive to break the "governance gridlock" within the organisation.
Its 12-strong executive board is also set to be scrapped and the committee structure is also set to be abandoned under the review which is being conducted by George Reid, the former presiding officer of the Scottish Parliament.
Senior managers within the trust, which is currently headed by the chief executive, Kate Mavor, will be urged to form a new "directorate".
Interim reports issued by Mr Reid in the run-up to his final review being published next month have revealed the full extent of NTS's troubles and the scale of "fundamental reform" he believes is required over a five-year period.
His most recent report states: "The trust's grossly inflated governance structures impede setting a clear strategic direction and are the main barrier to renewal of the organisation."
Mr Reid said an overhaul of the trust's management was "the fulcrum for change needed to initiate and inspired a five-year programme of reinvigoration of NTS".
"At the moment, the trust has a two-tier management structure. It would be better served with the one board of trustees, mainly elected by the members, but also including several trustees who would be appointed for their wide experience in a certain field, such as finance or conservation," he said. "It's the kind of model which is standard practice for charities in the UK."
Officials running the troubled heritage body have admitted the organisation has been "overspending for years", cannot afford to improve flagship sites and has suffered from a culture of complacency towards fundraising.
Despite attracting a record number of members last year, they have admitted the organisation may have to shed some of its 130 sites, even those that have been gifted to the nation, as it is saddled with "too large an estate with too few people".
Bosses have pledged to back a "total modernisation" of the trust, Scotland's largest charity, which was established in 1931, but has been dogged by financial troubles in recent years. It ordered the review last autumn after a financial black hole of almost 13 million led to it cutting 45 jobs and mothballing four sites.
NTS faced a revolt from grass-roots members after the charity revealed it would be closing 11 sites and shedding 91 jobs in an effort to save cash. Its plans were later scaled back.
The senior management's report for the review revealed the trust had become financially dependent on "unpredictable income", such as legacies and investment funds, and was now reliant on the sale of assets.
"We are effectively emptying our piggy banks", it states.
A senior insider at NTS said: "The ongoing strategic review has been welcomed by senior management at the trust, and it is very much seen as a catalyst for change.
"There is general agreement that the current governance structure is not the best way forward."