The ideal replacement would reproduce as many of alcohol’s positive qualities as possible. It would act as a social lubricant by reducing inhibitions. It would produce feelings of euphoria. Users would be able to control their level of intoxication by limiting their consumption. Finally, it would integrate seamlessly into the existing social structure, served in drinkform at bars and other gatherings alongside traditional alcoholic beverages.
I honestly don't think there will ever be a safe replacement for alcohol, in that I think what draws many to alcohol is the fact that it is dangerous. There are few good examples of drugs that near-universally reduce people's inhibitions without inciting reckless behavior. GABA-ergic drugs are already going to have problems, in that they tend to severly inhibit people's cognitive faculties at recreational doses. MDMA might work in the short term, but the toxicity requires so much time in between uses that it's simply not feasible--not to mention, we're finding more and more evidence of lasting effects. Just about every dopamine-based drug I can think of will promote reckless behavior at higher doses. I do think psychedelics such as LSD and 2-CB would be awesome candidates if we lived in a more altruistic society; unfortunately, not only are these illegal, but taking them socially often results in the user suddenly becoming all to aware of the malicious, hierarchical, and manipulative undertones to our social interactions. In fact I'd argue that alcohol isn't as much a social lubricant as it is a social anesthetic.
It seems odd to me that alcohol is rated so much higher than heroin on the scale this article presents. I understand it intellectually, but not instinctually.... If you can call a learned attitude an instinct. Interesting fact, though, that support this article's assertion: alcohol, unlike most substances, can kill during withdrawal. Withdrawal from most other drugs merely makes you feel like shit.