Our sponsors Bannermans do off-the-peg by-laws (see ad at top of page) or you could join OCN and see if they have anything you might need.
As for the other apartment, by not having a by-law in place, your neighbour has cleverly (or perhaps naively) made the owners corp – that’s you and all the other owners – liable for any consequences of their wall removal should the unit ever be sold.
Your strata manager should quietly offer to allow them to have a by-law transferring resonsibility passed retrospectively. And maybe you and the neighbour could split the cost on what would be a virtually identical by-law.