The reason why I chose no other female superstar but Lacey Evans is that Evans herself has issued a kind of warning to the 24/7 Champion, R-Truth on Twitter. It is highly unlikely that WWE will book a title change off TV, but given that the company wants the fans to talk about the title all the time, the WWE Universe will not be surprised if the title changes hands on a flight, at a bar or even at live events.
Coming back to the Lacey Evans thing, the former NXT Superstar has her eyes set on R-Truth and it is likely that she will become the first ever female 24/7 Champion. WWE often uses social media to build up future feuds and rivalries hence, this could be one amongst them.
The fact that Lacey Evans lost her RAW Women's Championship match at Money In The Bank and two tag team matches on RAW and SmackDown Live could be WWE's way of signaling the fans that she is done with Becky Lynch.
Since Lacey is not a part of the women's tag team division, the best way WWE could utilize her is as a lower mid-carder. And to win the 24/7 Championship is the dream of every lower mid-carder.