Mono is too heavy and have millions other dependencies I dont want to grab.
Running a modern & practical functional language on RB Pi will be extremely joyful for me.
sudo apt-get install fsharp
[...]
Need to get 22.2 MB of archives.
After this operation, 66.0 MB of additional disk space will be used.
Remember that the 10MB figure for CoreCLR you give is just for the runtime alone, it doesn't include any class libraries. The Mono runtime is in the same ballpark.
It was targeted mostly towards very low-specced hardware, closer to a Arduino than a Pi.
I'm guessing things like F# relies on too much things which are not included here.