I was thinking of some file types that afaik don't exist.
One is filesystem entries of files stored in memory from disk files, updated when the disk file modification time changes. This would be a big disk-access optimization in some cases.
OS development is a major undertaking, it's not the sort of thing you can do in a weekend, especially considering it requires low-level programming techniques that are avoided in modern application development. The appeal of things like Linux and BSD is that the hard work is already done for you, but unlike Windows or Apple operating systems you have the freedom to modify the user interface (which is all most people really care about, messing around "under the hood" is really only called for when working with embedded systems or mainframes, where you need to get every last bit of performance out of the machine - and only low level programming specialists really have the ability to effectively optimize in those areas, anyway). And the UNIX architecture, although rather old, wasn't really made for "mainframes", one of its main advantages at the time was that it could run on lower-end systems.
All sort of things require low-level programming.
I think I understand your idea.
How about a daemon that handles that stuff? You give the daemon the name of a script and of a fifo. Your daemon calls inotify on the fifo and waits. When one of the registered fifos is open, the daemon triggers the script with it's output descriptor directed to the fifo.
It is an idea that has already been implemented at the socket level: inetd. It is a system that spawns a specified process when a connection to a port/socket has been opened. No fancy inotify crap.
Is that supposed to make it any simpler?
UNIX and C are highly overrated. They were made popular by commie students who liked to share software.
There were systems prior and after UNIX which were made better - MULTICS, IBM MVS, DEC VMS, etc
Systems for personal computers have nothing to do with unix too.