I see the following options:
- Add custom Edit- & DisplayForms (not sure if this works, tough)
- Develop & depoly a WebPart, use SPRibbon.TrimById to remove the attachments-button from the ribbon, add the WebPart to the Edit-&DisplayForm
well i had to do it through css on displayform
as no other options was there for me and my EditForm was custom so i just kicked that attachment field from it.