Of course can this be a feature request! You can easily submit it as a separate request (which would be the preferred way), via "ask related question" above.
The alternative way of doing this kind of arcs, where the arc is only on a single edge, actually *is* easier to achieve and would also be more in line with what is supported already.
If you could add a sketch of what the exclusion arc should look like on an edge to your feature request, that would be great. You can't, however, add an edge with such an element to a palette--custom edges are not supported.