Toggle between left and right orientation in the editor
Pretty self explanatory. Add a settings area, and one of the options could be to toggle between whether the stage is on the left side or the right side.

Lockable outlines
In 2.0, when you resize a vector shape, the outlines change thickness too. I suggest a toggle on the outlines, so you could choose whether they'd maintain their thickness, or change it with the shape.

Outline Gradients
Maybe restore the ability to add gradients to outlines.

Restore some deleted sprites
There are several deleted sprites in the sprite library. I think they should be added back.

Add the Scratch font back to the font menu
The Scratch font is still in 3.0, but is inaccessible from the font menu. It should be readded.

Dropdown on the toolbar
I think you should add a dropdown arrow (v) to the toolbar, so the forum and other pages can be accessed without scrolling down.

when green flag clicked
forever
if <(evil kumquats) > [0]> then 
stop [evil kumquats v]

  

else
update signature
end
[/scratchblocks]

If I didn't write about some features, it means I'm neutral about it.

Outline Gradients
Oooh, yes! This would make perfect optical illusions

Restore some deleted sprites
Can you name some?

Add the Scratch font back
Oh, I never noticed it was gone. But why is it gone? @ST I know you don't own this font, but it is your signature font! ADD IT BACK

Dropdown on the toolbar
I don't completely agree on a dropdown but I do agree putting the forums and the wiki back on top. This would be useful for many Scratchers. (Maybe make a toggle for those who support it?)

Toggle between left and right orientation in the editor
I think this should not only be in costume editor, but in the code.
Examples:

mirror over [X] axis across [some sprite's center]

mirror over [Y] axis across [some coordinate]

clear mirror

Lockable outlines
Yeah, this is a problem when shrinking or growing vector sprites. Part of why I prefer Bitmap.

Outline Gradients
Yes please!

Restore some deleted sprites
I'm unfamiliar so I have no opinion

Add the Scratch font back to the font menu
YESSSSS!!!!!

Dropdown on the toolbar
I'm confused by what this was supposed to mean.

All in all, SUPPORT!

<<behind [sprite1 v]? :: sensing> and (layer :: looks)>

stay awesome :: #FF1493

Please make a separate post for each suggestion so that each one gets the attention that it deserves.

1. No Support, you can already change the orientation of the editor with javascript.
2. Support
3. Support
4. No Support, you can always find those sprites online, and Scratch has enough sprites as it is.
5. What would that look like? Please elaborate.

Scratch Team had some copyright issues with the Scratch font (unfortunately, I can't find the link), so I don't think that they'll bring it back.