Sorry, I deleted my initial answer.
How you want to do it is impossible. You probably shouldn't dwell on trying to do it with sharepoint list at all.
Infopath "Sharepoint List Form", in contrast to other types of templates (for ex., published to form/doc libraries, is hard-linked to its (BTW, one only and the same) sharepoint entity = sharepoint list.
You cannot separate (or change to other list) creation/updating of Sharepoint List Form once you started it except unlinking the form from its sharepoint list.
And there are very specific and restricted ways of linking/creating this form like:
- pressing "Customize Form" button on ribbon in browser having navigated to a sharepoint list
- pressing "Sharepoint List" in Infopath Designer (File > New)
- in Sharepoint Designer 2010, navigate to sharepoint list and press Design Forms in Infopath > Item on ribbon