By way of alternative and If not

If not and by way of alternative are semantically related. In some cases you can use "If not" instead an adverb phrase "By way of alternative".

If not adverb - Perhaps; indicating possibility of being more remarkable (greater or better or sooner) than.

By way of alternative and if not are semantically related. You can use "By way of alternative" instead an adverb phrase "If not".