Lui is a chunky player and strong. He can hit in D as a result. What he isn't is fleet of foot and really pacy - it is just the type of 6 he is.
If we want a different style of 6 we need a different player, not some mythological transformation of an existing one which is never going to happen.
Same with Hurrell - we signed what we signed. These are mature professionals who've been in the game since their teens. Whatever potential they were going to have, they have had the time to reach it. Very rare to see a mature player transform - what tends to happen is a young player gradually develops physically into their mid-20s and then it's a fight against decrepitude