> The filesystem doesn't support it.

Remember that Linux supports hierarchical mounts! You can mount anything at any depth of directory nesting. Even if it were true that MAX_PATH were an FS limitation, you could still nest mounts and encounter absolute paths exceeding MAX_PATH. MAX_PATH is simply the length in bytes of the longest string you should expect system calls to accept as a path parameter.

> I use Linux computer with 16Mb of RAM, total. Of course they don't run systemd nowadays since it's too big, but in my opinion systemd is good, and I would like to see it more in the embedded world.

It sounds like using systemd is a terrible idea for memory-constrained devices, so you really don’t want to see it in the embedded world.