If you really want to sit in front, consider using miles for the trip. Even if 1 y pax per ever 100 got op-up'd (which is greater than the actual op-up rate), it would seem that picking your routing on a 1 in 100 shot of an upgrade isn't really worth it.

If you're truly indifferent to your routing, then I guess it's worth it (as a DM, you'll be near the front of the queue for an op-up if it were to happen, but even as DM, you don't know you'll be top of the queue), but anything other than the most direct routing sounds like potentially a bunch of unnecessary flying (in Y) in hopes of a long-shot occurrence.

If you are leaving from an AF gateway city, perhaps see if they have y to y+ upgrades available (they don't have a minimum m fare requirement for the upgrade), then connect back to London.

If low-fare international upgrades are of importance to you, note that AA doesn't have a fare class requirement (beyond being a published fare) to use SWUs. If this (low fare economy traffic overseas), will be a repeating theme for you, if you can redirect your travel over there, you'll find this difference to be very valuable.