IMG have suggested a group stage in the CC early on and I'd tentatively agree with that.
You could have say groups of 3 with an SL team, Championship team and League 1 team with 1 or 2 going through. This could replace a preseason friendly, and for lower league clubs it might be a good pay day if they have weeks to sell tickets for an SL team coming to town.
You'd still very likely end up with the same teams going through, but the advantage is fixtures can be finalised well in advance which helps ticket sales. Id prefer that to loop games in SL, at least there would be some different matchups.
Should be straight knock out SL clubs should be in the draw earlier than this weeks draw . You'd still get the same attendance if Hull payed York regardless if it were in a group stage or knock out comp.