2) Go back to the main roster to pursue a mid-card title
Whether you can see it or not, Lio Rush is solid mid-card material. Remember how many times The Miz won the Intercontinental Championship? He maintained mid-card status and his credibility through the Intercontinental Championship. People like Shinsuke Nakamura have credibility too, but Rush is someone that has a much longer future in wrestling and deserves at least one shot at a mid-card title some time between now and his retirement, whenever that may be.
Seeing Lio Rush as United States Champion or Intercontinental Champion would be fun to watch. It's always cool to see the smaller guy stand up against all the odds thrown his way and come out on top of the mountain as champion. To see that same little guy defend his belt against bigger, stronger opponents and hold his own through the storm would be something to keep fans hot for him for a while.
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Having Lio Rush do that on a mid-card level would solidify his position on the main roster and may be one of the things to watch for on SmackDown or RAW.