The radical recommendation is among 62 wide-ranging proposals from the group, which is led by former Church of Scotland Moderator Dr Alison Elliot.
Dr Elliot's Land Reform Review Group (LRRG), says that ministers should establish such a maximum in law, to achieve their declared goal of "a fairer, or wider and more equitable, distribution of land in Scotland ... with greater diversity of land ownership."
The 260-page document, The Land of Scotland and the Common Good, seeks to establish provisions in the public interest, where necessary backed by law.
Other recommendations include the abolition of District Salmon Fishing Boards and giving the Government and local authorities first refusal on land coming on to the market, when this would be in the public interest.
It calls for local authorities to have the right to serve a compulsory sale order in a vacant land area, and for community councils or other local groups to be able to ask the council to do this.
It seeks to establish who exactly owns what and to introduce measures to stop vast tracts of land being held by anonymous companies outwith the EU.
The laws of succession, which protect landholdings from being split up, should be changed, leading to an increase in the number of landowners.
Meanwhile, a Community Land Agency with a range of powers should be created to "support and deliver" an increase in local community landowners.
There is a call for Crown Estate Commissioners to depart Scotland and their powers devolved while "serious consideration" should be given to introducing a system of land-value taxation, which could be an alternative to the council tax. However, ministers quickly ruled this out.
Dr Elliot said: "What we need to see is policy and decision-making taking greater account of the public interest, opening up land ownership to more people and giving communities more influence over land use.
"There are weaknesses in the market and contradictions in public policy that must be addressed if we are to see the kind of reforms that will modernise Scotland's approach to land ownership and use."
Scottish Gamekeepers Association Chairman Alex Hogg said: "While some of the proposals are sensible, there is no denying this is a state-centred programme of recommendations which, if implemented, would greatly discourage private investment in Scotland. Naturally, this will place a major burden on Scottish tax-payers as we seek to re-circulate a smaller pot of money. If the state cannot foot the cost, our members' jobs on the hills and rivers are at stake."
Land reform campaigner Andy Wightman said: "There is in fact not one [of the recommendations] which is anything other than plain common sense."
David Cameron, chairman of Community Land Scotland, the umbrella organisation for community landowners, said: "We welcome support for the principle of a land agency to secure more community ownership."
Douglas McAdam, Chief Executive of Scottish Land & Estates, which represents landowners, said it appeared to be biased against private landowners. He added: "It makes a series of unfounded recommendations that will create more publicly funded bodies, increase bureaucracy and place an even heavier burden on the public purse."
A spokesperson for The Crown Estate said: "We were happy to respond to the Land Reform Review Group consultation, as well as meet with the group and provide detailed information on our activity, including our increased community engagement, which has led to a step change in locally driven projects delivering economic benefits to coastal communities. We will consider the report in detail in due course."