I don't see this as a big overhead. It is more a problem for ordering, but internally, wikidata could store a "midpoint" value for intervals where no explicit central value is given, and use these for ordering purposes.
Well, I would call that "mid point" simple "the value", and the range would be the accuracy. There's an important conceptual distinction here to having ranges as actual values.
Can this conceptually distinguish between a meaningful midpoint value, and one that is useful for ordering, but has no meaning and should not be displayed as a result value? See the examples on
https://meta.wikimedia.org/wiki/Talk:Wikidata/Development/Representing_value...
Gregor
PS: With accuracy you introduce a new concept here which was not in the representing values paper (see http://en.wikipedia.org/wiki/Accuracy_and_precision). This is different from confidence interval ("uncertainty") where it is not yet decided whether the value indicates accuracy or dispersion. Confidence interval is a measure of Accuracy only if the sample measurements are normally distributed and if no systematic bias exist. --- I believe it is important that wikidata is flexible enought so it can capture both, especially because in many cases dispersion is used as a rough estimate for otherwise unknown accuracy, and since in many cases there is no "true single value" and the dispersion is systematic (see e.g. car model length example).