This is a good idea, but I have a couple of questions:
1) Isn't it better to replace elite lockeds with mythic and arcane shards? Of course, recipes for mythics and arcanes should be made as soon.
2) Shouldn't it consist of only 1 level, with elite boss? For example, let's see at Kraken Mines. People don't run lvl1 and 2, only lvl3. The same thing can be here, people won't run 1-4 levels, only 5th one, so making it only 1-leveled would be quite reasonable.
3) Should it be better than arena? I think, arena is the best place to farm elite chests. Let's imagine we have two equal parties. First farms arena, second farms elite dungeon. After hour of hard work, first party will kill ~20 bosses and get 5-6 goldens for a whole party. Second party will make 2-3 (assuming that elite dungeon is pretty hard) runs and get what? I think, loot table should be more various to be better than arena.