If I understand correctly you want to limit the type of widgets differently for each section? But you can only limit it per area..
The problem with that is that there is also logic from within Kentico. You can change a section-type. Say you change section 2 to Section 1 (meaning lose 1 zone) from the image above. Kentico automatically moves widgets to the next available zone.
Also the "allowed widgets" is to be used as a guide and not a limitation. If the widget was placed it won't be removed when you change the allowed widgets param.