User blog comment:Master Sima Yi/Assassinews 03-12-'14 — New Assassin's Creed in Victorian London leaked/@comment-4786308-20150106171334/@comment-3046679-20150112155115

It looks like they took the grenade launcher from Rogue and made that into a purely shrapnel weapon.

And I doubt you'll have customization in this DLC other than some bare-bones stuff.