No.
In regards to the stabilizing the exchanges, they basically need to stabilize the pool (the % of sick people vs. healthy people). Once the insurance companies have this information, they should be able to price their products so as to make a profit.
How do you do this?
In regards to rising costs, I can think of a few options though they all seem unappealing (price control certain things or ration care), so you need a creative solution to that.
The more sick people covered (the goal of the ACA, recall, was to force healthy people onto the market that would otherwise choose NOT to be, so they could pay into insurance to cover the costs of sick people - all the while making sick and healthy people pay the same for their insurance, all the while making it cheaper for all involved), the more expensive overall coverage would be.
Since you can't ask people who we KNOW will cost a hell of a lot more to pay a hell of a lot more, you must make everyone else pay a good bit more to cover the costs of the people who cost a hell of a lot more.
If you remove the mandate, thus giving people the choice to be in the market or not, you take away the source of funds from people who cost you little or nothing, thereby making it even MORE expensive for all.
The real answer is to remove the mandate, remove the restrictions on varying charges based on actuarial charts of costs, and remove the restrictions on who may sell where. Meanwhile, give us back our health savings accounts as tax-free, and while you're at it make it a tax write-off for individuals purchasing insurance just like it is for companies, and I think you'll see the cost curve bend down for 95+% of people, while the cost of health insurance will necessarily rise for those people who we know will cost a lot. Make donating to these people's health care costs tax deductable, and I think you'll see the bulk of the problem go away.