Thanks for your wishlist.
Things like undo/layers have been intentionally left out.
Alchemy is a bit odd in this sense because the focus is on the
process as opposed to making a final artwork.
Therefore rather that make functionality that allows you to 'perfect' a single work, it is more about expanding the options for artists at the start of the process. Ideally you should be able to generate a range of 'starting point' shapes/images which can then be polished up in photoshop or your weapon of choice.
Keep in mind this is the general concept/stance and we are trying to make this a community process, so nothing is fixed in stone. Originally in Alpha 01 everything was black & white, with colour introduced later on!
Mirror slider( that lets me change where i want the mirroring to begging on the canvas )
If I understand correctly, this is already there - the Move button in the Mirror module.
using external shapes similar to the font tool but from small images/patterns.
This is on the cards, we have already started coding it up... but it does not yet work

color pick for foreground and background.
Good idea!