Great suggestions, i like most of it without any coments ...
Except:
6) THE HOTBAR IS TOO SMALL
the hotbar could be bigger so we have 4 - 6 more squares.
4-6 is nothing ...
I mean it would be nothing on max level.

I would certainly +1 option to expand AND reduce our hotbar ... both horizontaly, AND verticaly ...
See no problem in it.
If you want 3 Row hotbar ... have it ... if you want 4 ... have it ... if you want just 1 ... hey, its your interface do whatever you want with it.

Same goes horizontaly ... you want it as tiny as possible? Make it shorter ... you want to expand it to full size of your monitor? Sure, why not.
Question is, if we should get additional "lock" for size of our hotbar ... (lets call this compromise)
If it should be adjustable in menu ... (my preffered option)
Or if it should be adjustable any time with no way to lock it ... (worse option imho)
Dragon Age: Origins did this, and it was awesome. :3
23) HOTBAR - ONE ICON FOR SPELLS FROM MULTIPLE SOURCES Great idea +1!
Except i would give there also scrolls for that spell ...
There is no reason in my opinion to have Magic Missiles, and Magic Missiles from neckage, and Magic missiles scroll ... those are 3 icons for the same cast.
Lets include it all ... Magic missiles > here are all your aviable sources of this spell.