The idea of TATTOO YOU Deluxe is a funny one. An album made of old archive material in the first place. So basically they could use anything they did 1972-81 as potential material for it... (doesn't much differ from EXILE basically).
Anyway, I wonder if there really is some left-overs from those sessions Jagger made alone (finishing the songs melodically and lyrically)? Or was the case that they had already picked up the ones that would make the album, and nothing else was touched?
Theoretically thinking, Jagger could take anything they recorded 1972-81 and then add his bit there, like he did with EXILE and SOME GIRLS. Now, that would sound even approriate, since it actually is mimicking the actual making of TATTOO YOU...
Anyway, the idea is so funny that most probably it will come true... and TATTOO YOU bonus album will cover anything they did in Pathe Marconi 1977-83, teh left-overs from SOME to UNDERCOVER, a'la "Its A Lie". And it will be a good one!