Tailoring a Sportscoat

[76classic]

I am looking for a little input. I wear a 48 regular in a jacket due to my chest, arms, and shoulders being an athletic build. Problem is, I'm smaller through the waist, so the jacket tends to billow...making me look bigger than I really am. Going down a size is not an option because I wouldn't be able to squeeze into the jacket. Can an off the rack jacket be tailored without destroying the jacket?

 

[DocHolliday]

Yes, the waist can easily be nipped in/shaped, to a degree.

 

[Styk33]

Just like altering a jacket in a suit.