Throstur,
To answer your question:
Is it somehow possible to tell the Entity Model to leave unbound table properties totally alone and ignore them totally in insert and update?
No, it is not possible.
Unfortunatelly, that's something that can't be done in the Entity Framework.
DevForce runs on top of the Entity Framework and has minimal control over either EF or the EF provider’s SQL generation.
You already found the 2 possible ways of solving this problem: manually editing the edmx or creating stored procs for the inserts.
If you adopt the first approach, I suggest writing a script that does the changes in the edmx xml, so you can run it after you regenerate your model.
As for the latter, you will have more work upfront creating the stored procs, but it will require less maintenance.
Kind regards,
Silvio.