JMoff,
The NCAA can grant a waiver for any reason, but the scenario you presented would not typically result in a hardship waiver to allow a 6th calendar year. You can read about it in 14.2.1.5.1, which says that a waiver may be granted if the player misses two seasons for reasons beyond the player's or institution's control. Two season ending injuries or illness, extreme financial difficulties, flood or earthquake, or clearly erroneous written advice from an institutional academic authority regarding academic ineligibility all may lead to a waiver. Taking a redshirt year is specifically cited as not a reason to grant a waiver.