The ECB should print money, but they most certainly should not use it to buy long term debt.
Why not?
Because it has distortionary effects. The central bank should limit itself to the nominal side of the economy. Having it buy long-term debt would bring it into the real side, and give the privileged whom the central bank would buy debt from into an unwarranted advantage. It would also create all sorts of incentives for rent-seeking. Besides, there is no need to as the current monetary policy tools are more than enough to do the job.
Yes, I don't see why there is any need to create debt in a deflationary environment, as any spending can be just done with fiat currency printed up for the occasion.