NAV: Use of "Places to Avoid"

I've entered a few places into the Nav's "Places to avoid" list. No problem; I just create a point or small area over a road I don't want to use for routing.

Be advised that the Nav will not use any of these places if you ask for a detour! I just ran a test here in town and proved this. I created an "avoid" area, getting routed a different way as expected. I then asked for a detour, knowing that there was no other road except the avoided area. Sure enough, I got a message saying "Unable to calculate route."

Here's a new feature we need: A way for a detour to use avoided areas if necessary.

This would work:

1. You press Map View and Detour.
2. The Nav attempts to compute a detour as usual.
3. If an avoided area can be used for the detour, the Nav asks if it can use the avoided area.
4. If you say OK, the Nav calculates the detour course using the avoided area. If you say NO, then the detour might be longer, or it might fail to calculate.

Why is this important? Because, if I have several avoided roads, there are times when the Nav could fail to provide a detour. Since it doesn't advise me that the avoided roads are needed for a detour---that I've made it impossible to detour without those roads---I'm left without a viable detour option.