I came across the SOIL-initiative which aims to create a Single Open Intermediate Language. I believe perhaps if there is a collaboration with this initiative it might be of mutual benefit for this project also. This can help further research in IR, optimisation of IR, better targeting of web and other platforms, inter-language operability, etc.
Since Nim targets C/C++ the benefits may be as much as other languages. Perhaps as SOIL matures Nim can target SOIL IR.
I'm sorry, but I don't think Nim should consider targeting SOIL at this point. It seems to be in a design stage, and doesn't have exact answers for how it will solve problems of current IR representations, it just promises that "it will be better". Also it seems to be heavily geared towards the web, which I think is not a good thing.
It reminded me of https://xkcd.com/927/ again.
This idea is almost as old as I am (it does predate my entry into programming by a few years): https://en.wikipedia.org/wiki/UNCOL
Nim (that is, Araq) made a wise choice and targeted the closest thing to it: C
While I am 100% sure @jibal already knows, it perhaps bears mention for others that the idea has had many incarnations -- only a tiny fraction of which are on that Wikipedia page. Things like SUIF, C--, the internals of practically any retargetable compiler, and on and on. The Wikipedia page itself mentions a bunch of ideas floated in 1954, 4 years before UNCOL itself.
The idea is probably as old ">1 CPU ISAs" and compilers themselves. The number of incarnations might be the number of production class retargetable compilers divided by like 1.05. This seems not to stop groups of academics from getting grant after grant to "do it right this time" which is what SOIL looks like. ;-)
LLVM would probably be a better way to go in 2020, but that's been discussed before, too if you search for it on the forum, @sirinath.
Nim (that is, Araq) made a wise choice and targeted the closest thing to it: C
Heh, IMO .NET is actually the closest thing to it, it supports many dynamic features, it supports GC, it supports reflection and value based datatypes. Yes, it's from Microsoft so now we need webassembly instead. But that's politics, it has nothing to do with technology.