Say, for shits and giggles, that you can do this with every part of the body (including the head) without serious issue (like replacing the brain, memory, etc.)

First week: cut off an arm and replace it.
Second week: cut off other arm and replace it.
Third and fourth: legs.
Fifth: torso
Sixth: head

Question is:
Is this person still considered viable food? Sentient (yet), metahuman (yes), alive (yes).

Are they still the same person? See the Ship of Theseus.

It's implied that Tamanous is in financial trouble from their heyday of a decade ago, due to the fact that bioware and therapeutic cloning have come down in cost over the last few years. However, they're not dead yet--I bet the fact that they have the logistics already set up is helping them stave off bankruptcy (since they've already sunk in the costs of setting up the supply lines for delivering stolen parts, which is something that bioware--and the inevitable regulatory climate that goes with a legal product--is likely still settling into), plus, they have blackmail and therefore leverage on all of the high powered movers and shakers that made use of their services before bioware came into more common use.

Also, they still serve some functions that cloning won't be able to replace, like mass test subjects for certain experiments; if it costs 40,000 per clone and takes two months to grow, and they won't be more than limp chunks of meat, versus a few thousand per head for some SINless street dwellers that'll be delivered in a week that you can implant and then drug/bribe/threaten/indoctrinate/etc to test out your drug/cyber/bio/etc, I know what your average soulless corp accountant is going to recommend that the experimenter use--at least at the proof of concept stage .

I was not aware that Tamanous had a hand in that pot as well. Still I'm not sure if an accountant would recommned that. How can you justify lots of money paid for a trial run for whatever you try to develop without any documented test subjects.

If you make 'sapient' a requirement, what of someone who was born brain-dead? At what point would the flesh of an unborn child turn into viable ghoul food? As far as clones go, you could argue that a certain basic 'grade' of clone needs to be used for it to still qualify as metahuman (after all, you can implant pig-parts in people and they wouldn't qualify), but there is nothing to that effect in the rules.

The only qualification for ghoul food that I have been able to find in the rules of any edition is 'metahuman flesh', though (and even so they can survive on fairly low amounts, as long as they eat other raw meats as a supplement).

As for Tamanous, they'll still fill the role of body disposal and ghoul feeders (which is actually a highly profitable endeavour: you can charge to dispose of the body, and you can charge for the meat you sell to ghouls), and I'm sure the second-hand cyber will never quite go out of style.

When it's already a black project, or your ethics-challenged bosses want to see if this new item is worth the multi-million investment needed to get it brought up to snuff, put through the rigorous testing and updating and so forth and then marketing. Or, put it this way: you're making the very first generation of Move By Wire implants. Do you, for your first metahuman test subject, use A) a wimp, B) a loyal corporate drone that the company has spent thousands on raising from the cradle, C) volunteers that you might have to compensate, or D) some poor schmuck off the streets, who, if he dies, you don't need to compensate anyone and you can just reclaim the cyber from?

Edit: Also, did a look through my copy of Augmentation. Pg 17, there's a little comment from Hannibelle about Tamenous' clientele and the stuff they cater (sometimes literally) to.

Reminds me of a high/low (milage may indeed vary!) point of the Wolverine comic, where said character survived a month long trip in a shipping container by cutting flesh off his own arm and eating it. Just shows that thermodynamics do not operate the same in the Marvel universe...