Shipping working binaries to Windows users from Linux is easier than shipping working binaries to Linux from Linux. :P
Oh right, wine... forgot that was a thing. Ugh, 32 bit emulation, 4 gigabyte address space, no code generation...
Maybe I'll try to figure out that niminst thing.
So, essentially, you want a silent installer? That can be done, although if you wanted to use the current installer code, you would need to add in some logic to sort out silent vs non-silent install modes.
If you want, you could just create a set-up directory of Nim and all it's bells/whistles on your own computer, then zip it up along with a batch script, and have them execute it.