Regarding your build, I wouldn’t put any points into Ranger because it isn’t that great. Also, if you are going to be using a Rifleman Com, you won’t really need any points in Overload. The magazine size buff from the com will most likely be enough for what you’ll need. You might also be able to get by without maxing Expertise.
So here’s your initial build (I’m assuming you meant to put 4 points into Preparation and not 3, since everything added up to L71):
http://bl2skills.com/commando.html#55155130005555515015104000000000
And here is what your build may look like if you decide to change it a little:
http://bl2skills.com/commando.html#55055145015305515010105050000000
I kept the skills that were important, but when I cut out the ones that weren’t (Overload, Ranger and Laser Sight), it gave me about 11 extra points. Since you are using a Grenadier Com, I put 5 points into Grenadier to give you more Fastballs. Since Double Up was available (and only 1 point), I picked that up, too. Finally, for the last 5 points, I invested them into Pressure, which is a great skill that can end up keeping you on your feet.
The weapons you listed are all really good, but I would recommend the Omen shotgun to replace the Blockhead. The Omen receives grenade damage boosts like the Blockhead does, and it also has more “oomph.” It comes in all elements, unlike the blockhead.
Keep in mind that these are just my opinions. Feel free to let us know how it goes.