Both essentially do the same thing: -20% lifestyle cost and +2 to resist poisons/toxins. One is a quality and one is a bioware enhancement.

I does not specifically say anywhere that they cannot both be taken on the same character, giving a hefty -40% cost of lifestyle. Any thoughts?

I would assume that the bioware replacement would be just that: a replacement. The effects of the previous organ would not be retained, only the effects of the new organ would apply.

This, of course, assumes that the digestive expansion is essentially a stomach replacement, and not just a modification to the entire digestive system, in which case, it could be possible to double up the effects, and reduce lifestyle costs by 20% twice (not 40% all at once, as the effects don't simply stack, but are applied subsequently) for example, lets say you're lifestyle costs are 1,000 a month. Ogre Stomach would bring that down to 800 , then Digestive Expansion would reduce that (resultant) cost by 20% down to 640 . Perhaps not as convenient as a complete 40% reduction (600 from 1,000 ), but still worth the hassle.

I don't think I'd allow it. If you have an Ogre Stomach, you can already digest all the stuff digestive expansion allows, right? Installing Digestive Expansion isn't going to increase the range any. In fact, you'd probably be cutting out much of the stomach and guts, to replace them with bioware versions, meaning you wouldn't have an "Ogre Stomach" any more.

Also, the 40% reduction to lifestyle costs would be ridiculous. Sure, you aren't paying for food (or, I suppose, much waste removal), but that's nowhere near 40% of most people's living expenses.

Also, I fail to see how being able to eat your couch warrants a break on your utilities and rent

I don't know how much trolls eat, but since they weigh in the 400-500 pound range, I think it's pretty easy to think 40% of their lifestyle costs could be food.

If you factor in the cost for troll-friendly housing (8 ffets ceilings are more a hit than miss proposition...), special furnitures, troll-sized clothing and just about everything else (try using an human-designed remotecontrol with troll fingers...) and odds are food won't represent more of their relative budget than what humans are using.

Maybe, maybe no. I always thought the flat 20% was kinda lame, myself. Personally I'd say use the advanced lifestyles system, and take a "lifestyle quality" that reflects the fact that you aren't buying any normal food as such. Would suck when you have guests over, neh?

Also, you might want to consider that, in some places, there's not gonna be much in the way of cheap non-synthetic organic material laying around. Out in the country, it would be great- you can eat wild plants. In the city, not so much; even the ogre stomach can't digest plastics.

Unless it's that new bio-compostable corn based plastic stuff, like Sun Chips is using...

*imagines a troll simply swallowing a bag of Sun Chips whole, without so much as chewing*