Why would you not use Flash villains in a Flash movie? Like, use it to build up his own universe instead of having him show off other versions of DC properties.
Like give me live-action Rogues with better budgeted and more comic-accurate costumes.
To be honest I don't think I'll ever be able to buy Miller as Barry, but that's just me.Maybe he'll evolve. Or maybe the alternative Barry is more like the regular one