Increase shaken pointer size So there is "shake mouse pointer to locate" feature which makes pointer bigger when I'm shaking it. What if I think it is not big enough? Can I somehow make "bigger" even more big? I couldn't find any settings in preferences but maybe there is some config I can edit. 

I don't want to change regular pointer size, only shaking one
You might have better luck with using a third party tool, like MouseScape 

I spent 2 hours just now trying to use Hopper to troubleshoot the System Preferences > Accessibility > Display Preference Pane while looking over the System files of the Mac to see if there is a config file that can be edited. It seems to me that the mouse is initialized with some API's like Appkit and CoreGraphics so doing more research with how to use these API's to edit your mouse is probably your way to go if you really want to do that. 

Otherwise, Mousescape could be your solution. Is there a reason you are trying to make it larger?