The 12 top-flight clubs yesterday unanimously agreed to push ahead with proposals to restructure Scottish football that include a 12-12-18 set-up to be put in place for next season.
Despite some individuals publicly wavering on the proposal in recent weeks, the monthly meeting at Hampden reached a consensus after all clubs were allowed an opportunity to say their piece.
The 30 SFL clubs will meet to discuss the plans, which involve a merger between the two organisations and a revamped financial distribution model, when they gather at Hampden on Thursday. No vote will be held, but there is likely to be an indication of the general feeling.
Both leagues would then hold a vote on implementing change, with the SPL needing an 11-1 majority and the SFL requiring 75% of the 29 voting members (Rangers only currently possess an associate membership), before detailed discussions will take place on writing a rule book for the new merged league.
Doncaster said: "SPL clubs were unanimous that this should be taken forward to the next stage and it's now over to the Scottish Football League clubs to give their views.
"No [other models were not put forward]. The next stage, assuming the green light on Thursday, is to agree a rule book that you would then get all of the clubs to vote on, perhaps in March, in time for a merger of the two organisations in the summer.
"There's a genuine desire for change. That can only be delivered if there's a consensus, and consensus means compromise.
"What's been put in front of the clubs is a package of changes that will lead to a pyramid structure for the game, much greater promotion and relegation from the first tier to the second tier, an all-through distribution formula, a single league body; all the things that tick a lot of people's boxes."
Rangers have been critical of the plans, since they and any other side that finishes in the promotion places in the Third Division will remain in the bottom 18 next season.
'I don't understand that concern," Doncaster said. "It would be far worse, surely, to put it back a year, when the whole of SFL3 would be playing a totally meaningless competition next year.
"Ultimately, the club that finishes top of SFL3 this season, who would be playing in the third tier of Scottish football next season if nothing happens, would still be playing in the third tier."
The chief executive was also asked if any SPL clubs had raised the issue of the cost of independent commission into whether or not Rangers' use of Employee Benefit Trusts breached registration rules, with the three-man panel chaired by Lord Nimmo Smith beginning its hearing today.
"There were allegations about a number of alleged breaches of SPL rules over a number of years," Doncaster said.
"Those allegations are complicated. The SPL board decided that the right way to deal with those allegations was to appoint an independent commission to establish whether in fact SPL rules were broken or not. And if they were, what punishment is appropriate – if any.
"I am not going to make any predictions about timescales."