And watch everybody avoid your lib. You think you are special? A competing lib will soon show up without that restriction. And that lib will get attention from corporations and they will have thousands of eyes use the lib and test it and beat the hell out of it and fix issues and send them upstream (since maintaining a fork is too much work) and eventually this commercial-permissive alternative will thrive and be 100x as stable and streamlined and your alternative will cease to exist.
But you are free to do this. Nobody prevents you from it. But please don't cry later when seeing effects that you don't like.
Assuming there are network effects for being the 'official' place to contribute to your project, than you can start with an MIT license, and once it gets popular, you take it private with slightly ever less permissible licenses.
(GPL wouldn't make this so easy.)
Fat chance. An average programmer will replace the library if the current one has issues, not fix the issues in the library. It is rational to do so (assuming a different lib exists, which it does for most libs).