My initial impression is that Boba Fett is to become the "Anti-Han Solo", which should make for some interesting story developments in the future. It'll also add a fresh dynamic to Boba's character and stories, seeing him work alongside a partner more closely than usual, opposed to being the lone gunslinger or only partnering up under extreme circumstances.
As for why Boba is partnered up with this wookiee - I believe it may have something to do with Boba rescuing this wookiee at an earlier date, although this isn't confirmed. Wookiee's during this time period are frequently enslaved by the Trandoshan species, who work under the empire and provide aforementioned wookiee's as slaves for the Imperial war machine. How this ties into Black Krrsantan, is due to the fact wookiee's feel obliged to enter into a "life debt" should someone ever save their life (which is why Chewie is so loyal to Han). Boba must have, at some point, saved this guy's life, making him eternally grateful.
How could this have come about? Boba isn't the type to go around saving innocents, however, I do have a theory. Bossk, a renowned wookiee hunter, who belongs to the Trandoshan species, must have gotten tangled up with Krrsantan at an earlier date. Whether this be through a bounty or a slave run, I'm not sure. Either way, Boba perhaps got stuck in the middle of this and, because of his rivalry with Bossk, sabotaged the Trandoshan's plans and in the process saved Krrsantan. Krrsantan initiates life debt, and here we are.
I think this is further supported by the fact that Boba kept wookiee braids on his shoulder at a later date. Boba isn't the sentimental type, but for whatever reason, he may lose his.. friend.. Krrsantan at some point and decide to keep a piece of him with him at all times, as a show of respect.
Again, this is just my speculation. I'd be interesting in hearing what anyone thinks.
As a side note, if anybody would like to join my recently formed crew, Don't Mind Boba, let me know below and I'll get you set up with a DMB title and sig. It's a Boba Fett fanclub.
__________________ “The galaxy must experience the pain of death and the rapture of rebirth as I have. I will bring chaos. It is time for war.”
Awww, you changed your title, "False Emperordmb" was awesome.
__________________ "Vader's pulse and breathing were machine-regulated, so they could not quicken; but something in his chest became more electric around his meetings with the Emperor; he could not say how. A feeling of fullness, of power, of dark and demon mastery -- of secret lusts, unrestrained passion, wild submission -- all these things were in Vader's heart as he neared his Emperor. These things and more."