Try this...

1. 
   
2. Creating a custom Content Type in MOSS (can be based on word doc, excel, etc)
   
3. Setup the document library to only accept the Content Type created in step 1.  When the site is templated, the doc library should retain the link to the Content Type.
   
4. Bind the Workflow process to the Content Type's creation.  Regardless where the content type is on the MOSS server, it should kickoff a new workflow everytime it's created.

I've never thought about that... I'll try!

Edit: just removed stupid comment due to my ignorance concerning the content types mechanism :-)

Ok, it works! Many thanks.

However, as usual, solving a problem brings another to light: I can't customize the ASP forms used in the different client events. I saw an old thread about this problem (the guy complained about the lack of Smart Form just like in K2.net 2003, and now I understand his pain) but no answer.

Originally, I wanted to use Infopath forms instead but the drop-down list is grayed out, ASP being selected by default in every Client Event I add.

Could you explain a little more about "can't customize the ASP forms"?    What are you trying to do?  There's no magic in the old SmartForms that you can't do with standard ASP.NET forms.

Hum... When you select "Advanced form", you can select the datafields you want to display, but

1. 
   
2. They don't appear in the form when I run a new process instance (the "K2 Blackpearl Datafields" section is empty)
   
3. There is no way to enhance the form, such as changing its layout, its style, the type of the fields (textbox, list, label, etc.)

And what about Infopath forms? Why isn't it possible to select such forms? I designed some processes with Windows Workflow Foundation and this was a feature.