Before 1.8.0, we could edit the block model that is rendered in inventory by going in a folder that is near to the textures folder. It was reset just when exporting and importing the workspace.
It seems that in 1.8.0 folders changed and models are now in the user folder. I tried to edit the item model of a block with custom 3d model so that block is rendered like an item when in inventory (like the hopper or the cauldron).
However, it seems that after recompilation this is reset.
So, I have a little idea: what about a button when making a block that lets you choose an item texture that will be rendered instead of the block when it is in the inventory? This way the user hasn't to lock the mod element/edit the model over and over.
This isn't very important but I think that it can be added easily in mcreator.
Sorry for bad English