Would it ever be possible to support modifying vanilla blocks, items, etc...

Sometimes a Minecraft mod doesn't just aim to add to Minecraft, but overhaul and change it - and it'd be really cool if it was possible to change the properties of vanilla block, entities, items, recipes, and more - including removing them entirely, if that's what the modder wants.

I think this is currently possible through Fabric, but incredibly difficult through Forge, so this could be exclusive to Fabric for a while.

I think this would really up the appeal of Mcreator, but I'm not oblivious to how difficult this may be.