A new group is to be set up to help devise a scheme which would give greater tax powers to Holyrood.
Think tank Reform Scotland is behind the group, which has support from opposition parties.
It will focus on the idea of "devolution plus" which would see the Scottish Parliament solely responsible for raising the money it spends.
Plans would stop short, however, of so-called "devo max" which would give Scotland full control over taxation.
The SNP has said it might offer a "devo max" alternative to independence on ballot papers in the referendum, which will take place in the second half of the five-year parliament.
Reform Scotland said the aim of the new group was not to draw up an alternative question for the independence referendum.
There is growing Unionist opinion that the ballot papers should only offer a straight Yes or No to independence.
Three MSPs are already said to be interested in the Reform Scotland initiative.
They are Labour's Malcolm Chisholm, former Liberal Democrat leader Tavish Scott and Alex Fergusson of the Scottish Conservatives.
The group will also include figures from business and civic Scotland.
It is likely the package proposed by the new group would go further than the plans currently being considered at Westminster.
The Scotland Bill, which the SNP opposes in its current state, would allow Holyrood to take charge of half of the income tax raised in Scotland.
However, Reform Scotland believes that does not go far enough and wants wider tax-raising powers to be handed to Holyrood.
Reform Scotland's "devolution plus" plan would see most welfare benefits being transferred, with state pensions, sickness and maternity pay staying at Westminster.