We’ve played with this idea a few times in the past in discord, but the gist is that we want some more challenging content, without giving the devs a ton of work by having to redesign and make new mechanics.
Can we get some simple ways to make shards harder? For example, the idea played around with was that you can use an effervescent shard to turn any 15 into a challenge shard. It would operate the same as a 15, but after every clear it would add 1 more random affix in addition to randomizing all affixes and the dungeon. This way, we could do harder and harder shards (eventually having every affix on one shard) without adding in any new mechanics, loot or shard levels.