(Of course, for GC'd languages, we will need aggregate types.)
In non-pointer C like languages, yes, they are mostly a burden.
The reason the .bc in the example given is large is because the toolchain does not try to optimize at all for intermediate .bc size. Final .bc size should be relatively sane.
I don't see that I can download the .bc files from that blog post, but I'm mildly curious if they are before or after running opt, because if i had to guess, based on the fact that it gzip's well, i'd guess it's before running opt on it.
But part of the reason you may find it worthless is because none of these VM's really perform the strong alias analysis and load/store redundancy removal techniques you could perform at runtime.
Maybe, maybe not. I've had parts of a precise, copying, compacting (commercial grade) garbage collector running under emscripten.
It "crashes" still, but seems viable.