More for Flower pots?

Why is it that Flower pots can only hold Plants; and why only some? 
Well why don't we make it so that we can use some more items/plants

Feather: Quill in "inkpots" for building?
Coral: these would fit perfectly inside a pot
Kelp: feel like it was left out so, it would be cool
Glow/Sweet Berries?
Nether Wart?
Chorus Fruit: would it display as a tiny chorus plant?
Amethyst in pots would look fabulous in builds, or even echo shards for display
(I wasn't going to include this but it's funny, so)
What about a Bone? It would be cool and useful for skeletal and other builds.
Here's a weird but funky one; Goat Horns, which would allow you to display and show off your horns
what about vines; Twisted, Weeping and Regular would display with a sort of pointed end twisting around.
Dripstone?
All of these are just suggestions; so please feel free to add to this idea in the comments, i'd love to see your ideas.