Wow ! Sorry for the disappointment. I did not think that W delta or AF made a difference. It used not to (but that was when A fare on AF were upgradable). Should you try call another agent and ask? Who knows?
The intra Europe leg should be be upgradable because only TATL flight can be upgraded.
If definitive that W Delta fare can't be upgraded (which is not clear from delta website), then it makes my 4 SWU useless again. I only chose them because I could upgrade W to O...