If you want to force it during booking then just use the multi-city option of any of the online booking engines.
Be aware that your desire to maximize time on Virgin America or JetBlue is going to work against you as those carriers do not interline well with other airlines (B6/AA can but that's basically it for domestic flights). This means you cannot buy a single ticket with TLH-ATL-JFK on DL and then JFK-LAS on B6.