Looks really deadly
Only thing to worry is that your BSB can have tough times surviving, no matter which hero you are using.. I don't if pegmaster can hang out with WE and survive cannon fire for long. Or hunt chaff/armour and grant reroll at the same time. Its gonna be hard to play him to full effect and make him survive.
If you keep your pegmaster BSB you might want to add gleaming pennant to other COB horde, or just give the standard to one of the DH. Then pegmaster would be free of responsibility and expandable. Obsidian trinket might be overkill, although 2+ vs magic sure is nice, but I guess enemies won't bother with cloak anyway