Blackbeard is not a coward, he simply knows when he's out of his depth…but to call him a thinking man is going a bit too far I think.
His ability is unique, but like people have said he has yet to master it, and with the new Gura Gura powers I don't think he wants to risk fighting with someone like Akainu who isn't exactly known for restraint.
Plus when you think about it, I don't believe there is anyone else on his crew ATM strong enough to take on Akainu, heck the fact that the Lvl 6 guys were in prison in the first place should tell you that they can't beat Admiral level fighters. Plus the ridiculous destructive power of Akainu's fruit mean's you dont really get second chances if you do engage in combat. So why risk it?
After all they wanted a battleship because those are supposedly big enough to be able to accommodate the Giant Squad Vice Admirals plus full crew on board. Not that many places in the world where yr gonna find a ship big enough to fit San Juan Wolf. For now they still have their ghetto raft so its not a real emergency.
Although I do agree that those guys are growing on me right now, they are true buccaneers, ornery, foul, unstable scallywags..just like real pirates. And the real Blackbeard LOL
Add to the fact that they basically got nothing to gain by taking Akainu out. They'd most likely suffer major casualties against Akainu. What would they have to gain from taking him out? More competition for PK throne? I'd rather keep Akainu thinning down the competition than to take him out and lose half of your crew.
They can do it later, when they get strong enough to handle him without major losses.