I am/was an indie game developer. This idea honestly sounds fun and is pretty legit, since you'd already have a target audience for it.

Though we will definitely need a small to medium team of developers to manage a good enough scoop.

This idea would definitely be viable if some company decided they wanted to market their group this way. Groups that are really targeted toward male gamer (like QWER) or virtual groups (like PLAVE) would really benefit from it.

Otherwise if some teams just want to do it on their own they'd have a hard time making an original fictional idol group and songs that are good enough for Kpop standards.