allow combination of checkboxes and numbered lists, as well as mix and match within a list
Simply combine what you already have, so you can have both a checkbox and a numberlist as well as within a list have either/or (checkboxes on some items, numbers on others, nothing on some or combinations).
Adminsashika (Admin, Checkvist) commented
Actually, you can combine different list styling in the same list - with smart syntax. Here's an example https://checkvist.com/p/59056
Is it what you need?