It takes a while to run the install script (~2 hours per USB stick). Perhaps a better option is to precreate an ISO image with all that software already installed. One option: https://www.linux-live.org/
The problem is that this respin does need to happen every time there are significant updates (e.g. Ubuntu 18.04.4 release), or else people would be exposed to security flaws. And it takes a while to create such respins (need to use a VM). On the other hand, it would make us truly have a Linux distribution of our own!