If you implement that, you instantaneously take away the ability to deploy applications through OS's automated deployment (like Kickstart, Jumpstart, or AutoYaST) and you create more work for every system engineer in existence because they have to finish your work for you, namely integration of your software (nim language) into the OS.
For every platform nim supports, native operating system package(s), delivering into /opt/nim (and system-wide configuration into /etc/opt/nim) should be provided. This is not some whim, it's a formal system engineering specification. See LSB FHS, /opt, /etc/opt and /var/opt sections, or the illumos filesystem(5) manual page for the same. (Why aren't you as a third party supposed to deliver software into /usr as you intend in that Github issue?)
If you do not do it this way, it will impede adoption because it's one thing for a developer to play around in a language and another for a system engineer to make it operational: system engineers' time is usually in extremely short supply, and if they have to package your language for you, they could easily just move on to writing software in a different language that they can mass-provision natively, and nim will stay an underdog. Operational maintainability is the end goal, means mass deployment without extra code or software like Docker, only using native subsystems. Sooner or later things must go into production.
Never bypass OS packaging. Unless you are an OS vendor, never deliver anywhere into /usr, not even /usr/local.