What if we take it one step further: apply the template of a specific category to all of its subcategories, unless that subcategory itself uses a customized template.

Example: We have category A/ using the default template; category A/B/ with a modified template, and hence all categories under it (A/B/C, A/B/D. etc.) using the same template. However, there is a A/B/M which itself has a customized template, that it (together with its subcategories) uses. Or, there is a a category A/B/C/N/ that has its own template (remember that A/B/C has inherited the A/B template) that it uses together with its own subcategories (A/B/C/D/N/O), sub-subcategories, and so on. In other words, categories inherit their parent's (or parent's parent) template, unless specified otherwise.

Is this already available or feasible to attain with rather decent programming skills?

Sorry if my post is not crystal clear - I'm not a native English speaker.