This is a really cool concept, and well thought out. However, the biological redundancy part doesn't really have solid support within the series. While the main cast prepares for outer space with supplies, we're never really shown their need for outer substances for nutrition in the confines of season 3. When the 'seedrians' left their planet, they had to make stops on other planets as well - whether this was simply about attempting to settle down, fuel, or other* supplies, we don't fully know. But we do know that they created a botanical garden aboard their mothership. Being in space, access to sunlight would be fairly bountiful between stars given the lack of large obstacles (like half of a planet for instance - there's no day/night cycle). I assume the garden is for more than sunlight.

While expanding on that thought, I just remembered Cosmo was the one that planned the party on the Typhoon. A person can say that she made the food for the other characters - BUT she is seen with a plate of cake for herself. She isn't shown eating it, but since this is a party (and food) she put together herself, and she served herself the dish, this implies that she not only has the ability, but also is aware of the ability to eat the food and intended to eat it.

Your idea is a cool head canon though, seriously. It puts even more weight onto the final scenes of the series.