Have an application option or something to disable the automatic scaling and more importantly moving of sketch features as you are attempting to dimension and constrain them.. More often than not the logic of the functionality doesn't do what the user wants nor expects. This often causes more mouse clicks and time to adjust back to the intended placement.
To be clear.. This is not about leaving degrees of freedom or not fully constraining sketches.. This happens during the process of attempting to full constrain a sketch.
There are very few cases where this functionality actually helps a user.. More often than not its a negative experience.
Here is one post discussing this silly functionality..
http://forums.autodesk.com/t5/inventor-general-discussion/why-sketch-moves-if-dimensioned-after-bein...
Here is a screencast showing how it will move 2 sketch points almost off the screen for some reason as I'm attempting to dimension it.. Causing me to have to leave the dimension command and drag it back to the approximate location so I can then complete the dimensions again..
Here is a quick photoshop of a simple check box that could be added to disable this in the application options..
"Disable Automatic Sketch Adjustments (scale/position) "... Something like that would be nice to prevent this unwanted movement.