A DM/PM can look at the seat map (start doing a dummy booking since delta.dumb won't let us see seat maps for other cabins now) and only request the "upgrade" if window seats are available. Then watch for the "upgrade" and immediately change your seat if needed. If you cannot select a C+ window seat then, you would need to call DL to cancel the C+ "upgrade" ASAP so that you can hopefully get your former seat back. If the "upgrade" doesn't clear fast and the C+ windows are gone, you need to cancel your "upgrade" request to avoid being stuck in a middle seat.

However, on your flight (domestic red eye), what specific benefits do you expect to get from C+? Free drinks? Enhanced snack basket? Less legroom than in your exit row seat? Are these benefits for you worth the risk of a bad C+ seat and the hassle of monitoring the "upgrade" and seat assignments?