If he's fully capable of 4-betting a wide range putting him all in with a strong hand is an option for me QA or better, Pocket 9's or better. I'd be unlikely to risk a large proportion of my stack at 120BB for a marginal spot though as its a huge advantage.
my usual indications in an MTT is the 4-bet is being used to either send a message he's strong and rep strength or he might not believe my 3-bet.. or thirdly to get an indication on your hand strength, If he was that strong holding a monster he wouldn't be to concerned about 4betting light for information. Most players like to either flat to hide strength or get it in with a big hand.
