It'd work fine, but unlocking them is different. Those are related to your multiplayer save file.
What I am talking about is how did they add banners for things like Hero of the Last days - those are Http based banners (not locally stored) which is why you'll notice it takes time for the banner to load in. Those banners were not added by a patch or DLC so somewhere, a setting is enabled to "unlock" them in the list of banner choices. Since no banners are automatically unlocked I'd have to take a look.
For reference this is the list of banners in the balance changes that as far as I am aware are not located in any DLC.
{
"Type": 2,
"Value": "(ID=150, BackgroundResource=\"ChallengeBanners/Halloween.dds\", srTitle=812513)"
},
{
"Type": 2,
"Value": "(ID=153, BackgroundResource=\"ChallengeBanners/N7Day.dds\", srTitle=813744)"
},
{
"Type": 2,
"Value": "(ID=154, BackgroundResource=\"ChallengeBanners/Bioware.dds\", srTitle=813603)"
},
{
"Type": 2,
"Value": "(ID=155, BackgroundResource=\"ChallengeBanners/Corsair.dds\", srTitle=813915)"
},
{
"Type": 2,
"Value": "(ID=157, BackgroundResource=\"ChallengeBanners/Prophecy.dds\",srTitle=814532)"
},
{
"Type": 2,
"Value": "(ID=206, BackgroundResource=\"ChallengeBanners/Punisher.dds\",srTitle=814545)"
},
{
"Type": 2,
"Value": "(ID=207, BackgroundResource=\"ChallengeBanners/MEMstrF.dds\", srTitle=778515)"
},
{
"Type": 2,
"Value": "(ID=208, BackgroundResource=\"ChallengeBanners/zaeed.dds\", srTitle=817835)"
},
{
"Type": 2,
"Value": "(ID=209, BackgroundResource=\"ChallengeBanners/ContestWinner1.dds\", srTitle=778529)"
},
{
"Type": 2,
"Value": "(ID=210, BackgroundResource=\"ChallengeBanners/ContestWinner2.dds\", srTitle=778529)"
},
{
"Type": 2,
"Value": "(ID=211, BackgroundResource=\"ChallengeBanners/ContestWinner3.dds\", srTitle=778522)"
},
{
"Type": 2,
"Value": "(ID=212, BackgroundResource=\"ChallengeBanners/ContestWinner4.dds\", srTitle=778522)"
},
{
"Type": 2,
"Value": "(ID=213, BackgroundResource=\"ChallengeBanners/ContestWinner5.dds\", srTitle=778531)"
},
{
"Type": 2,
"Value": "(ID=214, BackgroundResource=\"ChallengeBanners/ContestWinner6.dds\", srTitle=778526)"
},
{
"Type": 2,
"Value": "(ID=215, BackgroundResource=\"ChallengeBanners/ContestWinner7.dds\", srTitle=778516)"
},
{
"Type": 2,
"Value": "(ID=216, BackgroundResource=\"ChallengeBanners/ContestWinner8.dds\", srTitle=778518)"
},
{
"Type": 2,
"Value": "(ID=217, BackgroundResource=\"ChallengeBanners/ContestWinner9.dds\", srTitle=778538)"
},
{
"Type": 2,
"Value": "(ID=218, BackgroundResource=\"ChallengeBanners/ContestWinner10.dds\", srTitle=778539)"
},
{
"Type": 2,
"Value": "(ID=219, BackgroundResource=\"ChallengeBanners/VolusLover.dds\", srTitle=817851)"
},
{
"Type": 2,
"Value": "(ID=220, BackgroundResource=\"ChallengeBanners/FullTeam.dds\", srTitle=817847)"
}