Java edition: Custom blocks

Since resourcepacks define blocks and items in blockstate as well as defining their shapes in models, it should be possible to add a new block type "customblock" that can be added to the game without replacing any existing block for use in for example creative mode. Because it would be rather tedious and incredibly complex to allow fully custom blocks, I propose the ability to just add variations of existing blocks which you could also alter the behavior of through datapacks (possibly). For example, if I'd want to make a custom ladder, I'd copy the models/ladder.json and paste it to models/ladder-example.json and set it's parent to ladder, the texture could then be set to a texture found in your resource pack. The item id could either be set inside the ladder_example.json or the filename itself could be the Id. Of course, the ladder blockstate would also have to get the same principle in the founder blockstate, copy ladder.json and make a blockstate for ladder_example.json. At the start, such custom objects could be limited to creative mode with no possibility of retrieval in survival but in a future update they might be able to be added to the game even in survival. The motivation to add custom objects is mainly for building hence why it would be nice to have in at least creative.