Scratch

1. "clear sprite's pen"

I don't see how this wouldn't be possible. Many things would be simpler...

2. "Set frames per second to ( ), (frames per second), change frames per second by ( )"
This could be very helpful, and it will naturally slow down. Also it should have a minimum value...

3. "Pause sound [   ] until, pause sound [   ] for ( ) seconds"
You can't make a truly perfect pausing script without this.

4. Coordinate variables?
Hard to explain, basically storing a coordinate in a variable. So you would need a motion block called "coordinates". So you could do something like this with a list...
When green flag clicked
>forever
add [(coordinates)] to [list 1]
>end forever

And

When I receive [ replay ]
Set [some variable] to (0)
>repeat until <(some variable) = (length of [list 1])
go to [item [(some variable)] of [list 1]]
wait until <Key [space] pressed>
wait until <not<Key [space] pressed>>
change [some variable] by (1)
>end repeat

5. Pen round edges?
Basically a variable set to 1 or 0 (true or false) that decides wether a circle (rounded) or square (sharp) is drawn with pen down.