Suggestions I thought of today, which are three alternative ways to obtain tier 3 pieces other than from the Black Market auction house. I am suggesting these as I find it odd that randomness (if it appears on the Black Market AH or not) and gold are the only two key elements to get these tier pieces, when you can’t enter a raid to obtain them the natural way as it was removed a long time ago, despite that many of the other items offered on the Black Market AH are mostly all available ingame.
1: From my understanding some people think that there is a certain uniqueness about tier 3 pieces because everyone can’t get them, therefor the first suggestion is the one I think would succeed the most: It is to create a timeless challenge similar to the Mage Tower in Legion, where your ilvl, level and talents are restricted to a certain level and which at the end you are rewarded a full tier set, but only which your class can use. A theme for this can be anything, but personally I would prefer to keep a challenge like this to be done solo, to prevent commercial boosting ingame if it was a group challenge.
2: With Classic released with all the data from vanilla restored in that game, the data for Naxxramas 40 man can be restored for retail into the raid it used to be, and something a player can collect tier sets in (and possibly even all original transmog pieces. If Atiesh should be here as well can be debated). A suggestion is to make it a “normal level 60 raid” which a max level character can enter and one-shot everything, or a timewalking version which requires 40 people and where loot setting is set to personal.
3: Although uninspired, add a vendor which sell all the tier 3 pieces for a currency from some activity, or for gold. The price should be quite high and equal to what they usually cost on the Black Market AH.
These are just my suggestions, do reply if you have any similar idea(s)!