If you have a philosophy that you'll never have a ladder reset or an item wipe, how do you balance item progression? Even if you get 20x better drops, you are going to run into a problem of relative item progression vs time. You are still going to run into a problem where its going to be extraordinarily rare to get an upgrade at some point. What will keep you playing? You still have a personal time limit that you are willing to play for an upgrade.
If you're only going to make 1 character on softcore for PvM only, obviously, the game will eventually come to an end for you. The purpose behind softcore itself is for people that don't want to lose their gear/progression which a ladder reset every 6 months destroys. Ya, I know people don't have to do the ladder, but it does cause a schism between ladder and nonladder. I'd rather they hold events like PoE does time to time to give people more to do, week long ladder races, cut-throat races. Add in something similar to Gears Of War Horde Mode, add Gladiator style PvP events where softcore or hardcore characters can compete to the death for a prize pool.
Back on topic....I like many of your ideas and of course agree they need to add more choice between stats but I do think they can go further. Instead of necessarily having X item remove all mana cost for teleport and still buff many other parts and become a no brainer for teleport users. They need items like Trang Ouls that change the way a class behaves/opens up further builds. Example 1, you might find a wand that changes curses to auras or auras to curses + a few other mods. Example 2, equipped shield creates a "vortex" around you that pulls in monsters within "x" range or have a shield that creates a "wave of force" every 10 seconds to keep you from being surrounded. Example 3, "Zann Esu's Orb", wizard only, grants user 1 of 3 skills, Frozen Orb, Apocalypse(from D1 baby), or Lightning Nova. It would open up new ways to build your character that are interesting and fun while also paying tribute to its previous installments. Might be hard to balance, might not be hard, but either way, I like it.