Judging from that photo I would say its not a far stretch before that pattern morphs into the reverse question mark pattern on the supposed "grandjeani".
I am inclined to agree that Therea are Therea petriveriana variants. The only thing I wonder about is in my batch of Therea sp. "grandjeani", the males are usually quite a bit smaller than the females. Is this consistant with the variation or is it just a factor of the group that I have??
Also, my ranking (though it is a difficult choice):
1. Marcopanesthia rhinoceros
2. Gromphadorhina oblongata
3. Blaberus giganteus
4. Lucihormetica sp.
5. Therea sp.