I like the idea, but you shouldn't be able to craft ender dragon or wither spawners. Ender dragon or wither spawner in your house = complete destruction.
Why would anyone willingly put an ender dragon spawner in their house? I think it's just some way to commit massive scale grief.
Granted, I don't like it.
One, the spawner seems too easy to craft. For something that can spawn entities at a relatively low cost, it doesn't require much, does it? And soul sand as fuel? Just seems way too cheap.
Two, I don't like some of the mob spawner 'items'. They all make sense and such, (I think the emerald for villager spawn is ingenious) but some stuff like the coal for wither skellies is, once again, very inexpensive. And a red mushroom for mooshrooms is...eesh. Mooshrooms, in my humble opinion, should be found in Mushroom biomes, not out of an inexpensive trick to pull off.
In the end, it is just very overpowered and cheap. Some ideas in it are genius, but that's about it. If you make the fuel, items, and crafting recipe a little harder to obtain, then I'd support, but no.
I SUPPORTthis i think its a great idea ut wayyy to easy to make im thinking diamond for fuel Ghast tear for the mossycobble and emerald for the middle if this was harder to make then ya i support BTW NO ENDERDRAGON OR WITHER
Im not gona Not suport but the reason Mojang didn't add it because they want it to be a rare item that only spawns in dungeons and strongholds and in neatherfortresses! But i like the idea For creative use only for mapmakers