Could you add a server with the following features:
1. No auction house
2. No mailing
3. No trading
4. Learning a profession restores that profession to it's previous state.
I believe points 1, 2 and 3 already have support for hardcore players, and item 4 would just be a relatively simple server side change that just keeps both the current level and max level of previously trained professions and restores them to that level instead of 1/75 upon retraining. This approach avoids any client side issues with more than two professions.
Having absolutely no trading however will be annoying in dungeon raid groups, because the only way to distribute loot would be through need/greed/pass instead of allowing a master looter to distribute based on a predetermined system (e.g. rolls/SR). I believe hardcore players can trade within 5 levels of each other, but for a self-found server the point is to not allow this. But, under (non-solo) self-found rules it's considered okay to distribute raid loot within the raid group. The way allow in group/raid trading of only items obtained during the raid would be to just run a quick update on the internal database and set ALL items to soulbound. Then dungeon/raid groups can still roll for loot and distribute it because the two-hour trade window allows one to trade soulbound items obtained within the group but nothing else.
The final thing perhaps one could set up is ensuring that loot can't be distributed to effectively transfer funds, by doing the following:
1. When loot is automatically distributed within a group, whoever receives the splits the vendor price of that loot between the other group members, for example if someone in a 5 man group loots a 1s item, 20c is distributed to all other group members.
2. Any trades that are performed during the 2 hour trade window of dungeon loot ignore the gold in the trade window and instead result in a gold transfer of the difference in vendor price of the items on each side of the trade window, with a server side rejection if one side is short of funds to cover the difference.
These two rules could be completely implemented server side (as the server, not the client, controls the players inventory and gold in the end) and would ensure no workarounds to do gold trading between players.
The only other questions are regarding enchanting/lockboxes. Not sure how to go about these, arguably on a self-found server one should have to enchant one's own gear, much like a leatherworker or blacksmith can only make gear for themselves. For lockboxes, perhaps allow rogues to only open their own lockboxes, but perhaps buff skeleton keys, so that when opening lockboxes (and lockboxes only) they're not consumed, so non-rogues have a practical way of opening lockboxes (although it will require quite significant investment in blacksmithing).
It will be quite an unusual economy, as without trading one will need to directly interact with others to group up and farm required materials, so it probably should be a separate server. Perhaps a within 5 level grouping restriction should also apply like what is in hardcore to prevent what is obviously boosting.
Anyway just some thoughts, would be interested in seeing a server like this. Would be a very difference experience when you just can't go on the auction house and need to build your professions yourself, and rare recipes would be particularly special as they'd give your character a unique advantage.