Yep, because everyone who is going to do something interesting or enjoyable starts with the question "should I use language X because it's cool?". Look, I'm as

Yep, because everyone who is going to do something interesting or enjoyable starts with the question "should I use language X because it's cool?". Look, I'm as into cool FS-hacks as anyone, but writing a new filesystem has 99+ problems and the language used is either the last of them, or it isn't even in the set. Granted, you could (on Linux) write a little pseudo-filesystem (e.g. /proc or /sys) and not face any of the issues involved in extN or btrfs etc. I didn't get the sense that this was what the OP intended, but I could be wrong.