As a player, who has played a ton of Diablo 3, POE, Grim Dawn, etc , the most fun and exciting things to do in an ARPG is theory crafting.
I think what could skyrocket LE to popularity is the ability to craft ‘actual’ unique items, because I have never played a game that has allowed you to do that in a meaningful way.
My idea to go about it would be allow all crafted items to have 8 affixes, then separate the affix pool by weight, a regular affix would have a weight of one, rares’ are two and uniques’ are 3. Uniques’ are usually the items with special build defining stats so they are the only ones that can then be taken to the forge, broken down to a shard that’ll let you choose any one or two of it’s affixes to imprint onto the shard so that you can store it then craft it onto any base item.
This would mean a self crafted Unique item can have either 2 max Unique affixes and either 1 rare affix or 2 regular affixes, or just have 8 regular affixes etc. It will allow crafting to be entirely different from any other crafting system out there and will really push theory-crafting to infinity as more and more unique items (like in POE or Diablo 3) with build defining stats are released over the years. Now everyone can make their very own unique item and will allow any build to be viable and fun.
Just imagine how badass it will be to being able to plan out, theorize, and gradually build your very own item that is Unique to you alone.
I would also like to see dual wieldable one handed pistols and crossbows, two handed muskets, rifles and crossbows to be added because that would be fuckin cool (like in Grim Dawn).