That was intentionally removed because it's too powerful.
a new block called the "Armour Forge" allows putting potions on armor so when the armor is equipped, it'll give you that buff.
Same here, would be too powerful, like a beacon that you carry with you.
New Mobs should be added and only found in structures
That's too vague. What structures? What mobs? How do they look? What do they do? What their specialty that makes them a good part of the game?
[...] and illusioners turn into a spirit (a very useful mob)
Again, in what way useful?
The spirit protects you by killing enemies without you pressing anything (basically a very useful pet)
Like a dog?
new tomes : Shield of Mana (protection boost) Blade of Dark Magic (fires a blade at the nearest enemy) and Slash of Magic (just a normal attack, but better damage)
That also sounds too powerful, but it depends on the details.
It would only make sense if hoppers could feed the furnace fuel, and it is easy to make with commands but it really does feel like it was just not thought of
Hoppers can already put fuel into furnaces. Just put one on the side and it does exactly that.