Implement shortcut to switch between last two used tools (including layer, color, ...)

[eVoLuTiVeMEDIA]

example:

1. Draw a 0.8 black line in vector layer (tool A).
2. Select bitmap layer, chose a red brush with feather 100 and trace (tool B).
3. Press [TAB] and draw: You're now drawing on previous "vector layer" a 0.8 black line.
4. Press [TAB] and draw: You're now drawing on "bitmap layer" with 100 feather brush.

I think this feature would improve seriously the workflow.