I think that there is never a time when they would be more creative about routing (though I have had as great cooperation over the phone during massive IRROPS -- e.g., "OK, you tell me, what do you want to do...?"). Go up last to "collect", and I would bet a fortune that they will work with you. Do your homework ahead of time (sounds like you already have) as to what routing you would want - maybe ORD and DFW - and make it easy for them and you, in the event.

Also, last is the best position for getting them to give you the type of compensation you want. (I don't know if this is just an issue with UA, but most of us UA high-tiers want $ vouchers, while the standard DBC offer is a free ticket with restrictions. This is one of the tactics to tip the scale our way on this and other items -- like upgrades on the replacement flights. I digress.)