Peter writes:
Also, is there actually anything in ID theory(?) that precludes mulitple designers -- or in fact makes any comment on the number of designers necessary?
No there isn't.
Genuine 'Intelligent Design' arguments such as
Specified Complexity and
Irreducible Complexity make no comment on the number of designers required whatsoever. They simply conclude that there is a degree of complexity beyond which intelligent intervention is required.
These arguments have deep and serious flaws but they do not inherently or implicitly stipulate anything about the designer(s) beyond possessing intelligence.
Any conclusion or comment regarding the number of designers (whether single, multiple, comparable to the number of human designers or whatever else) requires additional assumptions.