I've seen one of these before. Unfortunately, if you don't create misc values for every velocity value (which you can already do), but instead you average out the velocity values to find the most human-like one, it will still lead to being one single standard speed. You are going to have to have a script load in every velocity value and randomly choose some on every motion, between every swipe of the mouse, etc. Also, a lot of people have mouses that require more of a swipe of the hand to get a smaller motion/bigger motion, etc. Mine is based on 3 settings that I can change with a button to speed up/slow down. If they can record coordinates of every mouse movement like people say they can, then how do we not know if they can record the speed option selected on the mouse. Furthermore, how do we not know if they record the mouse going off of the screen, and the outside movements we make like clicking on a specific tab in our browser. I know that running a Java Applet can allow access to anything on your system. So how do we know that if we are browsing the Internet while we are botting, that they can't see what we have open and how our mouse just so happens to be in 2 different places at once. There are just so many variables behind mouse movements that it becomes ridiculous. I just feel like that would be one huge script, not to mention the fact that there is a chance they don't even see our mouse's coordinates.
Also, as a hint on human behavior, A LOT of real people do what is called interface symmetry. I.E., they open up the stats tab to check on a skill, then they open up the prayer tab since it is symmetrical to the stats tab. Then go back to the inventory tab. Jagex made a factual estimate in 2009 that 38% of their players have some sort of OCD, or disorders alike that impact their gameplay in many ways.
Honestly, this is an extremely-small anti-ban feature. I doubt they even record our mouse movements because their ban-software has included creating 2 fake worlds to spy on botters (which they go around talking to you seeing if you are botting), and they also ban based on IP's previous ban-rates, etc. I don't think this small stuff really does much.
Nevertheless, I like what you are doing here.