How about a window, that appears, if a specific key is pressed,
Where you can type in a combination or a word to attack with a specific skill?
I think there would be no use for that. Hotkeys are way more easy.
Who said a game must be "easy"? There could be more than just pressing a key.
Game play and game controls are different things. Making a game difficult is one thing, but making it difficult to play is just bad.
Making players type spells would ostracize players who can't type well or fast. It would limit the appeal of your game to a smaller audience.
Maybe you could use combos instead to make the spell casting more complicated.
Yes, but what's with arrow keys or WSAD instead of letters? Typing in a specific arrow combination.
My opinion would be that using a skill like FF6's Blitz attacks with Sabin could be pretty cool, though I would steer clear of making it THE way to use skills in the game. That style of command, while fun for some (I always used Sabin :)), is not for many. It worked well in FF6 because you weren't forced into using it for the game. Some people just suck at quickly typing specific sequences of buttons, and many of these people are fans of RPG's for this reason, since that talent is not usually a requirement for one, but usually reserved for action/fighting type games.
As Boba Fett Link said, the appeal of your game would be limited if it was always required, so just keep that in mind. I would love to see "Blitz" style skills incorporated for certain characters, classes, or skills, though. :D