If you move from twitter thinking it'll not end up like twitter you're wrong. It'll go through the same growing pains process and you'll end up right back where you started with nothing to show for it.
No. The less code for a given set of functionality the better... often. Removing functionality just to reduce code is daft. Otherwise stop adding any features. Remove all features of the kernel until machines only just boot. Lot less code!
But that's true of all code in the kernel. If any change can break something then all broken bits will need fixing. Why not remove all drivers in case an update breaks them. Things can't be preemptively fixed before breaking changes are made. A driver can be complete and only need updating if someone else breaks stuff, so leave it alone until then and only remove it I'd no one comes to fix it.
Why clear them out if they still work and are useful? Seems like a backwards step. What's that phrase that people throw about:sometimes things are just done and don't need changing.
I've never heard anyone say ZFS broke, corrupted their data or failed in any way at all. With btrfs it's a consistent complaint. And btrfs literally has modes of operation that are known to be broken. I could understand if it was a new file system, but it can almost drink in pubs.
What's so magic about the number 100?