I do think we could be competitive in a P5 league, with P5 resources and recruiting, but we will never be LSU (nor would most BYU fans want to be LSU, since becoming so would require fundamentally changing what BYU is as an institution).
I think we can beat an LSU once or twice in 10 games on a neutral field, if we are playing well and some things go our way. This is part of the reason why I think the AAC would be advantageous: we would be playing the LSUs of the world in a NY6 game, with a month to prepare and after a fantastic season with good players. Not in the first week of September with a roster full of question marks.