I think language age is another point in support of your consistency argument. Older languages have had more massive library changes etc. whereas new languages

I think language age is another point in support of your consistency argument. Older languages have had more massive library changes etc. whereas new languages or unused languages have libraries change much less and therefore less churn. It's why Lua can be at one end and Boo at the other. Or C# and Vala despite their similarities. Old languages with lots of users at the low-churn end of the spectrum are something to look at though.