Syrian opposition activists, including National Coalition members, have drawn up a roadmap to achieve national reconciliation and justice for "all of Syria's victims," a statement said Tuesday.
The roadmap is to be presented in full on Wednesday, in the presence of National Coalition chief Ahmed 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 outlining the roadmap.
It comes amid reports of abuses carried out by both regime forces and rebel fighters in Syria's conflict.
While the country's uprising began with peaceful anti-government demonstrations in March 2011, it has turned in to a bloody war that has left more than 100,000 people dead.
The rebels have been accused of participating in various abuses, including summary executions and torture.
Forces fighting for Assad's regime, including the army and militia groups, have been accused of similar abuses, as well as sectarian massacres.
The proposals also call for disarming and restructuring Syrian security forces to uproot "corrupt officials".
"All armed groups will be disarmed, demobilized and reintegrated into Syrian society."
The roadmap also lays out plans for the country's political system after the fall of the Syrian regime, calling for a "hybrid presidential/parliamentary system."
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.
Syria's constitution privileges the legislature over the executive and states that the head of state must be a Muslim.
The group behind the proposal, Syrian Expert House, includes some 300 activists, lawyers and members of the opposition National Coalition and Syrian National Council.
Defected government officials and rebel commanders also participated in the drafting process, the group said.
The document is being released as fighting continues on the ground in Syria, with fierce battles in eastern Deir Ezzor and coastal Latakia, the home province of President Bashar al-Assad.
Despite advances, particularly in the country's north, Syria's rebels have not shown signs of being able to quickly win additional territory in the country.
Meanwhile international efforts to convene a conference to find a political solution to the conflict have stalled.
Syrian opposition proposes transition roadmap