Hi Shl
I have received ORC when I have suggested the routing but frustratingly, they may not rebook you until they know you are late arriving into Heathrow.
Regarding EU261, if you choose a routing that gets you there over 4 hours late in preference to one the airline chooses which gets you there within the 4 hour delay window, I recall posts or discussions that say the claim was denied as the chosen reroute was voluntary.
Might want to check JFK-PHX as no flights showing for sale after 11am tomorrow on aa.com