If I understand you correctly you're saying you'd take either AS or AA to DFW or ORD, then AA to LHR, then BA to MUC? If so, I'm pretty sure you cannot do that. If I understand correctly, AS's agreement with ALL of the partners is that you can combine AS and the partner in an award reservation, but you can never take 2 partners in one award reservation - even if they themselves are codeshare partners. In this case, you would not be able to connect to BA off of AA in LHR (I think). I'm sure someone will correct me if I'm wrong.

Now...to add one more option to your list: let's HOPE Iceland Air!! Rumor has it the agreement will be in effect soon. There were also rumors at one point about SAS, but I haven't heard this mentioned again for some time.