An artist's impression of the proposed new stadium
The Evening News revealed last week that Murray Estates wants to entice the two clubs to share a new 25,000-seat stadium on the land near Edinburgh Park.
Hearts have given a lukewarm response to the proposal so far, insisting that their priority remains to redevelop Tynecastle Stadium but admitting they would "explore any potential opportunities at Tynecastle or elsewhere in the west of Edinburgh".
The development firm today revealed that it has drawn up alternative proposals for its 20-year vision, in case the two clubs do not agree to share a stadium.
One option is a smaller community stadium - similar to the last Labour council's proposals for Sighthill - which could also provide a permanent home for Edinburgh Rugby, as well as local sports clubs and showpiece youth events.
Jestyn Davies, managing director at Murray Estates, said: "Hearts' focus is still Tynecastle, but they are still considering their options. I understand that and it may be that they do not come here. It may be that it is just Edinburgh Rugby that come here, or it may be neither.
"We commissioned a firm of architects to show how it could work and how it could be built on a staged basis. It could be a regional stadium where neither Hearts or Edinburgh Rugby play, and could instead be used for school or other regional finals. It could be a really important resource."
Over the last eight days, Murray Estates has held a series of workshops, seminars and presentations in one of Murrayfield Stadium's hospitality suites, giving local groups and companies the chance to give feedback on a masterplan for the 600-acre site between Edinburgh Park and the headquarters of Royal Bank of Scotland.
Other proposals for the site include 3500 homes and a new visitor attraction called The Calyx, seen as Scotland's answer to the Eden Project.
Councillors, however, have said the "garden district" plans ignore the fact that developing on the green belt is a hugely contentious issue. Council leader Jenny Dawe said she had been invited to the "charette" exercise at Murrayfield but said she would not be attending.
She said: "The advice was we should not be involved. The likelihood is that, because this is a breach of the green belt, it will come before the full council and the council itself will decide on it.
"No councillor can give an opinion on it as that would prevent their participation in the debate at full council.
"It is a huge project but the big issue is that it is a breach of the current status of the land."
However, Mr Davies said: "The city's own plans for growth show we need 70,000 new people in the city. That's potentially 30,000 households.
"Where will these people go? Edinburgh has a long history of developing flats, not family homes. This would be a proper, sustainable, planned community of affordable homes."
The plans were due to presented at Edinburgh College of Art tonight.