a bunch of transfers last season for FB you can see how they didn't grasp the offensive / defensive schemes well and it didn't really work. You saw the same thing with Colorado last season too.
I believe the exception is DTs and edge rushers. These positions in Jay Hill's defense don't need to learn as much or take as much on as the Safeties and the Linebackers do. It would be exciting if the staff were to bring in DTs / Edge Rushers in with only one year of elegibility remaining if they have experience and will help the team immediatley. The D-line is where BYU is lacking. Even if the Edge Rushers are used as 3rd down speacialists it would help immensley.
I'm sure the highly rated D-linemen in the portal are also wanting big NIL too which may also be a problem, but if they only had to pay for one year it wouldn't seem to be a big deal.