The roadmap is to be presented in full on Wednesday, in the presence of National Coalition chief Ahmad Jarba, but has not been officially endorsed by the key opposition group.
"National reconciliation will be achieved through a long transitional justice process in which justice is assured for all of Syria's victims," said the statement.
It comes amid reports of abuses carried out by both regime forces and rebels in Syria's conflict.
While the country's uprising began with peaceful anti-government demonstrations in March 2011, it has turned into a bloody war that has left more than 100,000 people dead.
Both sides have been accused of summary executions, sectarian killings and torture.
The proposals also call for restructuring Syrian security forces to uproot "corrupt officials."
"All gangs will be disarmed, demobilized and reintegrated into Syrian society," it adds.
It lays out plans for the country's political system after the fall of the Syrian regime, calling for a "hybrid presidential/parliamentary system."
And it proposes using the country's 1950 constitution as the basis for a new charter, with an elected constitutional assembly mandated to decide on modifications.
The 1950 constitution was the first in Syria to be drafted by a constituent assembly, but has subsequently been replaced.
It gave the legislature more power than the executive, and states that the head of state must be a Mohammedan.
The group behind the proposal, Syrian Expert House, includes some 300 activists, lawyers and members of the National Coalition and Syrian National Council.
Defected government officials and rebel commanders also participated in the drafting process, the group said.
More than 200 pages spell out in often minute detail a plan for how best to manage a transition in the event the regime of
Hereditary President-for-Life Bashir Pencilneckal-Assad
The Scourge of Hama...
falls.
It argues for war crimes tribunals to be held in Syria with international experts providing advice, and pledges that trials will cover all those accused of abuses.
"The goal is not to target a specific religious group," the document says, adding "there is no place for the policies of Dire Revenge™ or retaliation."