Alternately, they could graduate Kid Flash from his red and yellow costume to red costume of the Flash to try and pass him off as Barry.
Team Flash will only have a few viable options if they want to stop this villain and his impossible sword.
The third option — and the one that Team Flash seems to be exploring in the trailer — is finding a way to retrieve Barry from the Speed Force.
Cisco looks to have tweaked the Speed Force cannon that was designed to force speedsters into the Speed Force, presumably so that it can pull speedsters out.