I suggested this more traditional approach couple of days ago and people almost sent killers bees after me. Well, jokes aside, i think that after the Apple fiasco the best shot is to do exactly what you said, to focus on the first single. Concentrate all the efforts to make as many people as they can to have a listen to the new song. And the new song alone. All media will be talking about this new U2 song, their comeback, etc. But, always a but, have to be a strong, catchy tune. From what we have listened already, i believe TBT has a good shot of becoming a hit. Is catchy, and the message is as universal as it comes. Imagine the potential to insert that tittle in texts published everywhere. It's Beatiful Day all over again.
Not the bees!
Yeah, they really have to let the music do the talking for them. As you mention, they can get away from the Apple fiasco, and get away from the impression that they're a big, established monolithic band that has to make a big monolithic statement with every release (which is probably off-putting to a lot of youngsters, hipsters and others, but also presents the band with the colossal burden of living up to their 40 year reputation, and 5 year long silences between albums).
And ultimately, at the end of the day, all that matters is the music. If the single isn't strong enough and they do amazing publicity, it still won't be a hit. If the single is great and people enjoy it, and they have little or shit publicity, it will still likely be a hit.
It makes perfect sense for them to do something subdued this time round. Just play the song on the radio, play the remix in clubs, get it circulated in a way where it's saying "here's this cool new song", not "HERE'S THE NEW U2 SINGLE!!!".
None of this uploading to everyone's Apple accounts instantly, making a big deal about it being the biggest audience to ever receive an album.
I doubt anyone in the general public remembers the manner in which beautiful day was released. They just remember the song. Whereas, i bet a lot of the same people couldn't name a song off of SoI, but they could tell you how it was released (and how much they hated it).
I think being humble and staying away from grand statements is in their interest. And if the music is good enough, that's all they need.