He should stick to leafs because they are way nicer too play ESPECIALLY on Joust !
Joust may well be the game that requires the fastest tapping on one button and you're not going to get it as fast with a microswitch, let alone being it very uncomfortable. The good thing of leafs is that you can adjust them so let him have a look at them, maybe they need to be adjusted lightly. Also clean the contacts using a regular business card. Put it between the contacts, close the contact and wipe the card.
Also you can still get good quality leafs new.