Make something like a grasshopper with these changes:
-18650 (or bigger) removable battery\better battery life, if you wanna go ballsy put 2 batteries for double battery life, i saw ecig mods with 2 betteries and they were not big enough to be uncomfortable to keep in your hands and the mighty is pretty much considered one of the best vapes out there with 2 bis ass batteries, but this is more of a personal request, i'm sure 90% of people are ok with one battery and only having filthy 30 hits for battery
-bigger chamber with some accessory to do microdosing for people who care about that.
-way better cooling with standard (or optional glass) mouthpiece, who cares if it is a bit bigger? not everyone cares about hitting through a water piece, if a 100 dollars xmax 3 can have relatively smooth vapor, i'm sure you can study something similar aswell.
-More reliable than a grasshopper
-make the device as much as pure convection as you can, nobody wants their weed cooking for residual heat in the bowl when you are not hitting directly, use some material for the bowl that cool super fast or something.
-precise temp control from 100 to at least 250 C
-I personally always like a display over vibration to know what's up, even something minimal like the davinci IQ led solution.
-I guess many people here care about taste, so i guess the usual jargon like glass bowl\airpath, zirconia mouthpiece, ceramic capsules are all valid options to make flavour chasers interested, i personally ok with a stainless steel bowl (but i fear the forementioned residual heat with SS) but i like all glass vapor path and always liked the zirconia mouthpiece of the davinci devices, if retractable or with a magnetic cover to not damage it while not in use would be even better, but a simple glass mouthpiece is great too (remember to put some sort of cooling path)
Absolutely keep the 1-2 seconds heat time, the powerfull heater and not having to keep pressing a button while inhaling, a click to heat in 1-2 seconds and a click to turn off the device is perfection, you can still do the trick to turn off the device 2-3 sec before finishing the hit to cool down the chamber and suck up the residual vapor like all the other on demand devices, there is literally zero gains in having to keeping pressing a button instead of a click on\click off solution if the heater is super fast, only downsides like flimsy buttons that don't always register the input, more tearing\wearing on the fire button\uncomfortable when using a water piece, we only have 2 hands
Don't waste your time\money\design\inflate price with a session mode, there are hundreds of session vapes out there and so few projected from zero for on demand ONLY, but this is debatable, many people want both and i can understand that.
Form factor can be relatively bigger than a grasshopper, i'm sure people are gonna understand ( i do)
You can price a thing like this 300+ dollars and you are still gonna finish your first batch yesterday, it would be pretty much the perfect on demand device (and probably pretty hard to make)
I expect a beta unit in my mail very soon