Honestly, I don't think the game is coded to let people use the characters any other way. And given that F.A.N.G's theme still has the wrong loop point after 4 years, they're not going to recode anything more substantial than that unless they absolutely have to. lol
The code might not be the culprit here, or at least not the only one. In SFV, every DLC asset (characters, stages, etc.) are tied to your SFV account. You have to connect to the SFV servers at least once so it can confirm that you have indeed bought said DLC. After that you can use the DLC any time you want, even offline.
So even if everything had been on disc and there wasn't a code, you'd still wouldn't have been able to use the DLC until your internet is back.
Well that's irritating and kills it for me personally. Fortunately Walmart has a generous return policy as I'm just gonna take it back. Shame, as I wanted a "complete" version of SFV, something to play with even offline or if I take it to a family or friend's house. Guess I'll have to hope that Capcom will make a fighting game for the next generation that isn't some annoyingly put together package.