Here's the tl;dr:
Appearance and Appeal is very much GM discretion, though it's likely a stretch to say that food has smell or radiant heat, making it far less appealing that non-magical food.
It takes ~1-2 hours to eat a five course meal. It takes 30-60 minutes to package meals for distribution at production point, same for breakdown at service point. We're at 2-4 hours for centralize production, transport time excluded, and 1-2 hours on-premise production. Duration is based on Spellcasting rank, which likely is only 3-6 with 6 being uncommon. Therefore, in the best case, centralized production needs to be within 1-2 hours transport of the service point.
Finally, this spell has a range. Other than preventing the magician from spawning food in space, this can also be interpreted as 'the magician needs to be within range for the duration of the spell.'
Now, here's the sausage making...
Here's the spell text:
Weaving: 7 / 12
Range: 10 yards
Duration: Rank hours
Effect: WIL + 2
Wood. This spell converts any kind of plant material into a tasty feast. The spell requires three intact plants, no matter how scrawny.
The magician cuts or tears the plants into small pieces, then makes a Spellcasting (6) test. If successful, his Effect test determines the number of meals produced. Each meal has the following parts: appetizer, soup, salad, bread, entree, vegetable, and dessert. All of the meals are identical. Although they can appear to contain meat, none actually do. The meals are as nutritious and tasty as their real counterparts.
The spell only creates types of food that the magician has tasted within the last year and a day—a good reason for him to occasionally eat fine food to excess. Uneaten meals vanish when the spell ends.
Success Levels: Increase Effect (+2 Effect Step)
Extra Threads: Increase Duration (+2 hours), Increase Effect (+2 Effect Step)
Based on this, here are some of the critical pieces:
- Appearance: Very much GM discretion. The only things we have to go on are that it definitely starts as plant matter and "Although they can appear to contain meat, none actually do." I think that reading this statement to say the meal is a faithful reproduction of the original is over-reading. You can make a hamburger out of play dough (indeed, they have 'fun factories' for this) and it APPEARS to have meat, in the same way that an artisan-crafted tofu burger APPEARS to have meat, in the same way that a photo/video APPEARS to show something (e.g., we hear newscasters say things like this all the time: "it appears in this video that the man is stealing the hamburger"). All that is happening here is someone drawing an assumption from appearance and context - it does not imply more beyond that, specifically speaking.
- Appeal: This one's more iffy, but can't really fault a GM for expanding it. The only text we have is "The meals are as nutritious and tasty as their real counterparts." Since we are talking magic here, all logic goes out the window. It's entirely within reason that you could put this into your mouth, and despite being at room temperature, composed entirely of plant matter, and either stinking of a freshly mowed lawn or otherwise having no scent, it SUDDENLY has all of this as soon as it hits your tongue because these are all important elements of flavor. However, the only thing expressly noted is FLAVOR - the spell doesn't say that the food has the same aroma, the same temperature, or the same texture/consistency as the original food. IMHO, it's not fair to say "well, it TASTES like it's hot and oozing with juices and fragant, therefore it is also all these things even when not in your mouth" - we are talking magic, and the more you warp the magical word to force real-world logic onto it, the more you rob the magic of its magic-ness.
- Volume: Regardless of whether one thinks that an Adept, or someone with Adept-like powers, would spend their time mass producing food for profit, I think we can all agree that MINIMALLY, no one with a high Legendary status would be doing this. So, let's limit this to say RANK 6 in Threadweaving and Spellcasting, average STEP 6 in Perception and Will. We'll ignore extra threads since the idea of Adept-like people show up, and non-Adepts shouldn't receive Discipline-based extra thread powers. Step 12 Threadweaving over 3 threads means it'd take an average of three turns to cast (2 Threadweaving, followed by 1 Spellcasting). That leaves us with Step 12 on a Difficulty 6 roll, resulting in 1 extra success, meaning WIL+4 effect, resulting in an average of 10 meals produced. IIRC, we now have 10 second rounds, resulting in 2 casts per minute. So, in theory, this person could feed 100 people after five minutes of continuous (and I *DO* mean continuous) effort. Even if we assume they need a break equal to the amount of time spent whipping all this up, meaming 30 minutes casting and thirty minutes during an hour, we're talking 600 meals an hour. This is MORE than enough for a town and a small village. A single person MIGHT be able to support a large village (3 meals a day), but this is now what they do full time. For a city, you'd have multiple people working full time around the clock. This is straight numbers, so no real wiggle room for GMs, and this is assuming some pretty well powered Adepts or Adept-like people, who mathmatically should be in low supply (we're now talking in the hundreds from my early numbers).
- Distribution: Honestly, of all the things, I'd say this is the biggest problem with the idea of using Plant Feast for mass/centralized food production. The spell creates ready-to-consume food, meaning it is individually portioned and served food. Centralized food distribution relies heavily on bulk packaging, which we have completely lost. If the food is made off-premise, then it all must be carefully packaged into portable dishes, which take up much more space then bulk packages, and then carefully unpacked at the service point. Since no one is going to be moving individual meals, that means you have packaged food sitting around while the rest of the food is packaged for transport. I think it's fair to say this takes AT LEAST five minutes per meal, since you're not just throwing it into a box and hoping it comes out on the far side. Assuming you're shipping 12 meals at a time, which is pretty slow, you've lost an hour in preparation for transit and then an hour upon reception.
- Duration: As above, we have people with RANK 6 Spellcasting. That means that the point of production, plus distribution, plus service, plus consumption must all be within 6 hours. And, again, this is with mid-Journeyman powered Adepts, which is no slouch, and is much more likely to be 2-4 hours, based on 'Adept-like' people performing the service. A five course meal takes a good hour to consume, up to two if you're talking business/pleasure while doing it, and I can guarantee it'd be bad for business if the food someone bought disappears while they're eating it (which will happen, per the spell). So, we are now at 4 hours from production to service with the strong contenders, 0-2 hours for what is more likely. At this point, the idea of production from anywhere other than within the village/city is out of the question, it just isn't feasible from a time perspective. Worse, even centralized, off-premise production is basically out of the question as a further ~2 hours is lost in setup and teardown of distribution. Again, this is straight numbers, no real wiggle room for GMs.
- Range: Of all the things that say to me "Plant Feast is made for on-premise use", this is it. The spell has a RANGE of 10 yards. Other than keeping the magician from spawning food miles away, why does this spell even need a range? My argument would be that the magician needs to stay relatively close to the food (i.e., within 10 yards).