Customising bucket ranges in Map Visualisation?

Is is currently planned/possible to customise the ranges within the Map view ?

Numbers ranged
From a general data presentation point of view, the auto generated legend can be a bit painful, I would love to be able to determine where my buckets actually begin and end, as well as determining how many buckets I need (as the below is less than usefull)

Text Ranges

I am also looking to simplify further by mapping scores to words.
1 = Low
2 = Mid
3 = High

Is anything along these lines currently possible ?