No teasing anymore 
Ultimaker Mark2 - the dual-extrusion upgrade, based on my magnetic tool changer is finally there: http://ultimaker-mark2.com
Mark2 is an open community project. Will be interesting to see if people will adapt it to other printers.
@Arthur_Wolf might a cool smoothie feature ?
Nice! Good job on this
Smoothie already can do this because the toolchange is raw gCode. But a dedicated toolchange module to simplify the gCode would be awesome.
Well, in fact we’re already prepared for triple-extrusion without any additional loss of printing area. The only issue is this requires different electronics and 75% of the comfort of our solution, like x/y/z calibration wizards and on-the-fly fine tuning, is built into a special Marlin branch.
Edit : Never mind, I forgot that you can just set the offset in firmware setting 
Can Smoothieware do compensate for miss alignment between 2 interchangeable hotend?(Print part might be slightly off between 2 set)
Not in this configulation but 2 hotends that will have the same position like the one @Christopher_Hemmings do
To my experience offset compensation is a must and handled by most firmwares. But for the real deal you need comfortable menu-driven adjustment procedures (wizards) for tool head offsets, docking position, even on-the-fly fine-tuning of offsets and tool change retractions during print etc.
@Maxime_Favre We have been working for over a year on an extremely modular tool change module, it’s making good progress, and would make this sort of setup much simpler.
@Arthur_Wolf is it written enough that we can start testing?
@raykholo Nope
