Actually, the government didn't know he was Roger's son at the time they offered him that position. Right before we saw Whitebeard finding out Ace turned down the Shichibukai position, we saw Sengoku saying "Where did this kid come from.." because of how much trouble he was making. They offered him the position to quell the trouble he was making.ace is underated.....you should remember that when he made his debut, he was not just a super rookie(supernova), he was a super, super rookie (super supanova) the WG even offered him a seat in the shkibukai despite knowing he was the son of the PK. That should tell you alot!
saying that ace had no haki is wrong....in part 1, oda hadnt fully visualised the concept of haki.....and if you choose to stick to a 1 dimensional argument that he had no haki...it means you are simply saying he survived in theNW with no haki, how many characters have done that? it simply means he is OP
Also, Caesar survived in the New World for many many years with no Haki, we've seen tons of Dressrosa fodder who aren't fighters, they're living in the New World without Haki. Ace didn't need Haki because he had Whitebeard and his crew in his corner.
Because he was the son of Roger. And Ace had ample opportunities to use it and never did. All these excuses for Ace are becoming laughable.Ace has the highest confirmed bounty in the manga... Do you really think that he couldn't use haki?