Anyone who thinks that Morocco would ever allow the Sahrawi to control any of the territorys mineral or fishing wealth is seriously suffering from head-in-the-sand syndrome. It just wont happen. The Moroccan military, elite, and monarchy have been happily stealing Western Saharas abundant resources for over thirty years and are not about to relinquish their cash cow.
Why is Morocco proposing autonomy now after showing little or no interest in it for over 30 years?
I suspect that US pressure has something to do with it. The US was reportedly disgusted that Morocco refused to embrace Baker II. At the same time, US geopolitical and economic interests have led to increasingly close ties between the two countries (i.e. the US-Morocco Free Trade Agreement, the Trans-Saharan Counter-Terrorism Initiative (TSCTI), and the naming of Morocco as a major non-NATO ally). Much of the success of these initiatives depends on economic cooperation and regional integration in the Maghreb, and clearly the greatest obstacle to this is the unresolved Western Sahara situation. The US just wants the conflict resolved. And to Moroccos thinking, now with the Maghreb so prominent in US plans is probably as good a time as any to make a big push for a third way not including independence.
In addition, the Wests current obsession with the war on terrorism provides a smokescreen behind which Morocco feels it can slip one by the international community. By trying to appear the good guy with a seemingly generous plan for broad autonomy and by softening up world public opinion with an unprecedentedly aggressive and mendacious propaganda campaign (which brands the Polisario as a terrorist organization), Morocco is trying to exploit the window of opportunity provided by the war on terrorism. As long as terrorism is on the front page, Morocco feels it just might gain validation of its land grab through the back door, with the ruse of autonomy.
Finally, and probably most importantly, is oil. A discovery of oil off the Western Sahara would pose a huge dilemma. Economically, Morocco is suffering mightily from $60 plus oil and would want to exploit any finds as quickly as possible. Morocco obviously cannot exploit the oil by itself, but it is open to question whether international oil companies would be willing to drill for oil in a non-self-governing territory under illegal occupation. The big push for autonomy fits in neatly with the current Moroccan imperative to resolve the Western Sahara crisis but while retaining sovereign control of the land. And again, anyone who thinks that an autonomous Western Sahara would realize any economic benefits from oil off its territory has probably been smoking too much of the hashish that the Moroccan government and military habitually smuggle into Europe.
In conclusion, I just cant find any reasons to think that there is anything sincere or serious about Moroccos autonomy plan. They are floating it not because they want to, but either because they feel they have to or because they feel they just might get away with it.