The only ST RUSHER #1 - #4 on the punt return team are the front four and they should be LB or defensive lineman with a weight restriction of at least 230 lbs.
The rest of the players on punt return (including the wings) come from GUNNERS.
Any speedy CB (+90 speed) transitioned to LB should gain weight which slows them down. So if someone blocks a punt with a linebacker with 90 speed....somethings up because neither linebackers nor defensive lineman ever reach 90 speed. I believe LBs cap at 89 and they are the best of the best while defensive linemen rarely exceed 80-81.
To avoid any mistakes or whoops situation...all ST RUSHERS in the depth chart should be either LBs or defensive linemen so if due to injury or fatigue...ST RUSHER #10 who happens to be a CB doesnt line up and block a punt.
So the short answer is
ST RUSHER
LB or DE or DT with a minimum of 230 lbs.
GUNNERS
CB, SS, FS or any other fast player you want. The goal wasnt to completely remove the punt block...just stop the blatant use of speed on the front four to break the code.
Let's be honest here....if during an NFL game....4 speedy sub 200 pound guys lined up on the defensive line opposite 5 300 pound offensive linemen....most coaches wouldnt hesitate to call a direct snap inside run right up the gut....as long as it was 4th and 5 or 6 or less.
Anyway...that's my guidelines I'm using in my leagues