Changing the number of lines for the clefs would only result in easier "counting" early on in the learning process, and becomes unimportant when notes no longer represent a distance from a known note, but as notes unto themselves.
Even though the prospect of initially having to memorise only half of the notes, this amount of time is trivialised by the time it takes to get your fingers to respond by hitting the right note fluently.
Also, even easier than your proposed extra line would be to double the treble clef and indicate it's to be played 1 octave lower. I haven't seen this in mainstream teaching materials, and I surmise this isn't done because of the trivial time saved in the long run [1].
As for your second point: I strongly feel that for complex keys muscle memory and interval awareness trump extra visual information. In other words: if you are playing in a complex key, you should already have this awareness, and if you don't, you shouldn't be playing in this key.
There might be an interval between starting to learn a key, and becoming familiar with it, where extra information regarding the colour of the key might be useful, but I'm unsure if it outweighs the extra visual clutter, especially when considering that, when mastering a complex key, one presumably would have already mastered less complex keys, and already has a developed sense of muscle memory and considerable interval awareness.
[1] I have seen notes that have the value of the note imprinted on them. These are used mainly in children's teaching material, and are dropped fairly quickly after the concept of note-key correspondence is established.
Even though the prospect of initially having to memorise only half of the notes, this amount of time is trivialised by the time it takes to get your fingers to respond by hitting the right note fluently.
Also, even easier than your proposed extra line would be to double the treble clef and indicate it's to be played 1 octave lower. I haven't seen this in mainstream teaching materials, and I surmise this isn't done because of the trivial time saved in the long run [1].
As for your second point: I strongly feel that for complex keys muscle memory and interval awareness trump extra visual information. In other words: if you are playing in a complex key, you should already have this awareness, and if you don't, you shouldn't be playing in this key.
There might be an interval between starting to learn a key, and becoming familiar with it, where extra information regarding the colour of the key might be useful, but I'm unsure if it outweighs the extra visual clutter, especially when considering that, when mastering a complex key, one presumably would have already mastered less complex keys, and already has a developed sense of muscle memory and considerable interval awareness.
[1] I have seen notes that have the value of the note imprinted on them. These are used mainly in children's teaching material, and are dropped fairly quickly after the concept of note-key correspondence is established.