Elder guardian control core and spawnable/craftable elder guardians

So aside from getting prismarine for a conduit and an armor trim from the elder guardian, there is essentially 0 purpose to the ocean monument. You can go your entire playthrough without touching it and not noticing any difference. There's no unique loot, no special item, nothing. So I wanted to change that. There would be two different things to gather from a monument: 1: elder guardian components and 2: monument core. Monument cores only spawn one per monument and can be found at the very heart of a monument. Putting these items together, perhaps with a few other minor components, creates a guardian control core which also unlocks guardian crafting letting you make guardians similar to how you make golums, maybe with a special type of block you need to craft for it. Placing the core on its own does nothing. However, once you get your own guardians, they will patrol an area around wherever it is placed and defend said area from Any hostile mobs while being completely passive to you and other passive mobs. Granted, this would only really be useful for underwater bases and we dont got much underwater hoatile mobs, but still, at least it's something cool to give OM their own purpose.