I'm surprised none of the server community has picked up on this (as far as I remember), but we should have these commands added to the server where we can configure which blocks we can place on with the block you hold, or configure the blocks you can destroy with held item. This would very likely be integrated into the Itemizer plugin, since every other command that changed an item's behavior and content was categorized into said plugin.
I'll give you an example of the use of these: Player wants to have a stack of building blocks for combat and evasion. Player also wants to insure he/she cannot destroy other blocks around him/her, and wants a pickaxe to break the same blocks he/she is building with. Using these blocks and this pickaxe, which both contain the special attributes I request to add; he/she can go in /gma and be capable of building and breaking as the items are configured.
Another example is this: Player finds a puzzle dungeon that goes underground. The entrance sign tells Player to go to Adventure Mode to continue, and the Player follows accordingly. The dungeon has a multitude of puzzles that take advantage of this new feature, and the player has to place shulker boxes in the correct places, and has to find tools to break blocks that block the way of new tools, and so on until the path is clear. The Player likely enjoyed the dungeon because of it's puzzling mechanics and increasingly developing path, which grants the Player satisfying end results.
...AND ANOTHER ONE: Player likes to host a special country game where you dominate the game map defined by the borders of the games. Three other players join Player, and he/she has designed a special system where you can place these buildings, and they can only be placed on valid areas, so if a bridge was to be made, scaffoldings would be placed on water only, and drills would only be placed directly on top of ores. The game they are playing together in has more things going on than simply building a country, as now drills are necessary, where you need them to build more buildings, and also more drills to drill ores that you need for even more buildings and drills. Sometimes an ore is too hard to drill, so you'd need better drills, and some drills you'll need power from reactors and solar panels in order to drill. Materials you have are static on how many drills on ores you have, and their drill speed per second. (I would continue on, but you'd lose interest because of how advanced this kind of minigame would go.)
This kind of addition to the itemizer plugin would definitely remove the constant need to go into a local world just to generate a block/item with these attributes, which can go to the server through saved hotbars. I cannot stress you how many trips would be saved thanks to adding these commands in.
