nah thats high power incan territory. only IR leds emit much IR....not sure if a multi IR led would ligt a fire though lol.,,,invisible too so eye melting perhaps hehe
Even an IR LED isn't going to be setting fires anytime soon. Really, the color/wavelength is irrelevant as far as setting fire is concerned -- if the object you're trying to burn is black, or completely absorbs the color you're shining on it (ie, popping a red balloon with a green laser), the only relevant figure is the intensity of the beam in watts/square meter.
With incandescent, it's easy to get high power -- just buy a high wattage bulb, and it will radiate with almost 100% efficiency (most of that radiation is invisible, but that doesn't matter if all you need is a heat lamp)
LEDs, (and even HID lamps) don't radiate their excess waste heat however, they build up the heat internally -- usually requiring a separate heatsink. They're also limited to fairly low overall power, the only way to get high overall power would be with a large array, which would be almost impossible to concentrate enough to be able set anything on fire.
I prefer Xenon incan to LED for color rendering. This might not seem like a big deal, but be aware that the inferior color rendering of LEDs have practical consequences. For instance, depth, 3-dimensionality, and contrast are all affected, and for target acquisition - or even detailed rendering of one's environment, these are very important areas. Incans simply render the target area under the light better. Also, incans cut through fog far better than LEDs do. I use an incan for bump-in-the-night and emergency instances, and I use LEDs for everyday use when runtime and low battery replacement frequency are more important.
This is certainly the problem with the current LEDs, which are all blue emitters which convert a portion of that to green light. Red is almost completely absent, which is what causes most of the problem you've listed above (poor color rendering, depth perception etc). One trick that I have used in multi-emitter arrays with some success is to augment white LEDs, which tend to look "greenish", with separate red LEDs. I have found that dramatically improves color rendering/depth perception -- the beam itself looks a lot uglier, but the target being lit up looks better.
Also, in the case of fog, the shorter the wavelength (the more bluish) the more the light will get reflected back into your face -- I find if I hold the light as far away from my face as possible, their usability in fog improves. If I set the light down somewhere, and view my target from a different angle, the problem almost completely goes away (of course, that's hardly practical...)
IMHO some sort of RGB array has the potential to be the best -- the user could cut off blue completeley to produce amber light (for fog) or to have red light only (for night vision), or have white light of any color temperature, depending on the application. The only problem there is that green LEDs are FAR less efficient than red or blue -- which is why white is usually done using blue + a phosphor.
