I'm designing the menu for a website with three main sections. The main menu does not have sub-menus, and is used to navigate between the sections of the site. Since the different sections of the site are substantially different and all but one of the sections doesn't require a sub-menu for navigation, I'm not sure that the section menu needs to be in the header at all; also, putting the section menu in the header would require a redesign of the header across all sections.
The solution I am currently toying with is putting the section menu on the last element of the breadcrumb bar. Something like this:
The menu above is a hack on the Responsive Multi-Level Menu, which has a usable example here, the main difference being that I changed the trigger from a hamburger menu to a link. (I will also need to change the submenu trigger to the arrow, since otherwise pages with sub-menus are unreachable)
My question concerns usability, especially since I haven't seen menus in breadcrumbs before and I don't have access to UX testing. Will this approach create problems for users, and/or are there ways around those problems? (I'm not opposed to alternative suggestions in the comments)