I know that when creating a problem from an incident you can set defaults on the problem by updating the hidden elements within the frm002 form in detail_in.htmpl. Not sure if you could do a similar thing for change in the detail_in.htmpl by changing the button to a similar command. The problem is controlled by the following:
<PDM_MACRO name=button caption="Create Problem[!ea]" func="create_new('cr',0,0,0,'PRESET=type:P','INITFROM=frm002', 'PRESET=from_incident:$args.persistent_id')" hotkey_name="Create Problem[!ea]" id=ITIL_PROBLEM>