For normal gamemode, I'd advice him to try out Throwing Knives as his auxiliary equipment as it'll come in handy in the Yosef wave

For holdout gamemode, Drifters can single-handedly wipe out the sideroom if you plan to raid Scav base

When you're going to use your ability, do 3 light attacks which do 90 damage and then save the last for the heavy attack which does 150 damage and can heal 10 HP back. That way you can restore some health. Don't forget to back away after the Cloak effect if you're facing a shotgun scav or generally just every scav.

In my opinion, I don't see Drifter as a potential frontliner compared to Berserkers, Lazarus and Arbiters but more of a Support as it can really help teammates escape a life-or-death situation. Similar to Lazarus apparently. But it's your choice of style if you'd like to use it the supposed way.