Couple ideas

[Jalau]

Legendary tokens kinda destroy the idea behind legendary items being rare. We don't need bad and good items if everyone can just choose their item. I would suggest unlimited progress and create legendary items for different level ranges. This should cause players to sell their legendary because they might reach a point where the item is just bad for their level. Let's say Fiendish is a level 10 item. You can use it as you please but if you are level 40 even craftable items will be better than it. People would start selling their legendary items instead of hording them.

I think that would exacerbate the problem. 

That would make f-bow just about worthless as people that are "lvl 10" probably don't have much cash/wealth to get it and stag bow just stays the same ish price as most people with stag bow atm would not sell it as they would ether grind to lvl 40 or just be lvl 40 or higher. The problem is not people keeping their loot the problem comes when we have 100s of one thing but 1-5 of another.  People that have good stuff that have no reason to sell unless they want to change class or they want more gear but are willing to downgrade. Look at all the Warden locked bows other than the ones that got handed out in the event you would just about have no chance in buying one and its not just things that have a high value in this market even things like my Leviathan's Treads, Ornate Crusader Helmet, ... that have the same problem of low numbers. 

If you posted WTB: Leviathan's Treads 0 would sell to you unless you overpay a fuck tone... so you need to wait on one to drop but even then the line to get the thing keeps building and building. (but even then its a no from me and want to guess the same with nka)  

If by a small chance we do sell we can push the shit out of you to offer as much as you can. Is that fair? Yea because its "only one for sale". If you offer the same as we paid we and 110% not going to sell... So a good example now would be Mangler I guess... When I got it idk a year ago I paid 25m ish and from then there has always been about 0-1 for sale at a time pushing the price up and up and up (adding it got buff in 1.6.0) but my point is atm some people value the thing more than 50-60m. Is that on me for not selling no is that on anyone well yes but can you blame them for wanting more for what they paid? It's just good trading and no it's not a scam as they cant lie about a price when prices in the game are made on past trades (In some cases making them the last trader) to add people are crazy with wealth atm so some people can just "overpay" on thing and feel nothing.

For the new NI I would suggest pushing the level limit to like 100 and just making progress slower while adjusting the difficulty of the modes based on the average player level inside the run.