It's definitely a good idea.
But to implement this feature we would have to extend our templates ability with more selectors also based on the field type. After this, there will be a way how to extend configuration files similar to other templates ( http://help.skipper18.com/en/extending-templates ) like this:
<template element='field' use-case='datatype' selector='decimal'>
There are only two drawbacks. These templates will be applied after entity editor is closed, not directly when datatype will be changed. The second is that when user select "decimal", Skipper sets up scale to "10", but if user after that changes data type to "string", scale remains filled with "10" value unless "string" will have a new template.
Another approach is to implement brand new mechanism only for data types and move scale/precision directly to root properties ( ).
We will discuss it here more detailed what will be the best way and if it will be possible, we will try to implement it.