2:28 p.m. on November 3, 2006 (EST)
Like the Folkie, I would have to think about this one. My immediate reaction to the SAK (Swiss Army Knife) approach is that multipurpose widgets may do lots of things, but none of them well. The Swiss Army Knife is a prime example of that, as is the Leatherman, and all the imitations/copies of them. On your combination stove and light, such things sort of exist now - Camping Gaz/Bleuet has small stovetops that screw onto their proprietary canisters, and small lantern-tops, a couple of models of each. Primus has the same thing for the standard butane canisters, as does Optimus. At least one of the small butane lantern tops is "mantle-less". True, these are separate tops for the canisters, but many of the multi-tools have interchangeable bits.
Multi-use is all the rage these days in electronics - combination cell phone, MP3 player, camera, video (download movies or shoot your own), games, text message, email, I forget what else my latest cell phone does, but again none of them well, especially the basic phone functions (and this is a Motorola, supposedly one of the leaders in cell phones). Again an example of "lots of functions, none of them well".
Computers are sold these days as combinations of home entertainment centers, photo processors, business tools, and on and on. But the desk-top computer doesn't mate very well with a 60-inch plasma screen - totally different movie experiences.
Chefs have a variety of pots, pans, knives, spoons, forks, ladels, and other tools to prepare meals. Yeah, you can get by with a 1 liter pot and a spork. And the food will get cooked. But the "presentation" leaves a bit to be desired.
Fine wine in a sierra cup? Doesn't work.
On your stove-lantern combo, keep in mind that these don't just burn fuel. The stove needs to produce a wide range of controllable heat, distributed over the pot, while the lantern needs to produce light, with a controllable distribution from a moderately narrow beam to a wide area, without glare. Most fuels (compressed gas, white gas, kerosene, alcohol) burn with a blue, almost invisible flame when producing their heat most efficiently, where the human eye responds best to "white" light, a particular continuous distribution spectrum from blue through red. The wrong spectral distribution, and things look ghastly, or reading gets difficult (reading a map with yellow markings under a yellow sodium vapor light is almost impossible, for example). So lanterns use mantles in which the "ash" glows with a basically "black body" spectrum (the mantle-less ones use a wire mesh for the same thing).
One of the weirdest combination items I have seen is a plastic combination knife-fork-spoon. One end of the handle is a spork (ok, those sort of work), while the other end is a knife. Someone forgot that when you cut something, you often need to hold it down with a fork. A single combination of all doesn't work well at all, plus when you have sauce on the spork end and try to use the knife end, you get the sauce on your hands.
Not saying you can't come up with something. But think in terms of a "killer ap", as they say in the computer world. Something that really fills a need, not a "solution in search of a problem."