Oddly enough, the UFL abandoned the XFL-style kickoff rule and went back to the usual format.
This changes the kickoff strategy 100%. Now it's about making holes to run through. There's no second level so once you break through it's a foot race.
The old way. The XFL made you convert a 4th and 15 at your own 25 to retain possession. The NFL did not adopt that rule.
Just doing this in preseason is impractical. Preseason is when you work on plays for the upcoming season. Why put in all that work for a rule that goes away?