We know in the case of the WB pirates the specific division each wb commander had control over did not reflect their strength, it was assigned to them randomly or as a matter of convenience. The BB pirates forces are organized in a similar manner.
If there was meant to be a correlation between their strength and the fleet they commanded, then we would expect an ascending or descending order in terms of strength from the 1st to the 10th fleet. However, as shiryuu is the strongest and is neither the 1st nor the 10th we know this isn't the case. Back when we only knew Burgess' number, it was somewhat reasonable to think that perhaps they were numbered according to the order in which they joined Teach, however, with Shiryuu as no.2 that theory has also been proven false.
I don't think like the WB pirates there will be absolutely zero significance or meaning to the fleets the BB titans command, but that being the case, what could be the theme behind the numbers?
It is my belief, that the number of the fleet commanded corresponds to the each titans love and passion for combat. Burgess being no.1 makes perfect sense, as hes been shown several times to have a love for getting into fights, and since shiryuu was known to have butchered countless prisoners at ID him being no.2 seems to fit as well. As for Lafitte, he was noted to have been incredibly violent as a peacekeeper which could easily be consistent with the theme as well and while this is all loose speculation I think theres a slight possibility it could be right.
What are your thoughts on the numbering of the BB pirates?