I didn't know how to name this tool
but well, it's done.
What does it do:
Scales an object to fit an specified length. This length can be taken from another object, points or specified manually.
Translate an object by their bounding box centers, regardless of their center position.
Aspect = Keep Aspect Ratio.
BBoxC = Move by their bounding box center
Freeze Scaling = Freeze after scaling.
Local = Scale and Get BBox with local position.
Since SI can't do global scaling, if you scale with the global option, it will freeze the rotation before scaling, and after that, re-rotate the center to it's previous value.
It's an script so you won't be able to do one click-undo.