Does your ajax filter support spec attribute grouping? for example, country and region are two spec attributes, and I want to make country to be a parent of region. Maybe ajax filter is the not the right plugin, do you provide any plugin to support hierarchical relationship of spec attributes?
Actually the Ajax Filters do support this feature in terms of the required functionality but not exactly the way you have described it (visually and grouping).
I will give you an example. If you enable the Ajax Filters to be shown in dropdowns rather than with checkboxes then you will have 2 dropdowns: Country and Region.
Then if you select the Country you will get all the products that are from this country and in the Region dropdown you will see only the regions of the products that are returned (all the other regions will not be shown).
Basically the Ajax Filters check all the available options for all the specifications based on the Filtered products.
What you are trying to achieve is basically the same with the only difference that both dropdowns will be shown at the same time and not shown dynamically i.e select country then see the region dropdown.
Hope this helps!