Accuracy of resistance reading and the precise reading of temperature is not a real world objective, it's a technology objective.
OK, I think I am seeing your point now. So your ideal device would be something with a dial with an arbitrary scale, say 1-100 or blue to red, and it will fire any wire? I see no reason why that couldn't be done in principle, you'd just have to remember to use a low setting for SS, higher for Ti, higher for NiFe wires, and finally higher for Ni.
In theory, you'd have this if you had a device with a TCR set to around 0.003. You'd need a slightly expanded range to cover both SS and Ni properly. With a chip that normally does 100-300C, a TCR of 0.003 would just about prevent burning with SS (set at 100C) and just about get hot enough to vape with Ni (set at 300C). If you forget about SS, any currently available TC mod will be able to fire and control all wires in Ni mode.
There are a couple of issues with that though - loss of fine tuning ability and non-linear effects.
1. If your wire's actual TCR is lower than than the device "thinks", then you reduce the number of settings available in your normal vaping temperature range. For example, the normal 200-230C range (7 individual settings), might translate to the 150-170C range (5 settings) with the lower TCR wire. This is hard to explain without creating graphs, but this is what the maths says. You do get the opposite effect if the wire's actual TCR is higher than the mod "thinks" - you'd end up with more settings than usual in your vaping range. This is true for wires with a constant TCR (linear TCR profile).
2. Not all wires have linear TCR profiles in real life, Ni200 notably deviates significantly. This might result in strange things happening if you put a linear TCR wire on a mod expecting a non-linear TCR wire (or vice versa). NiFe30 (linear) on a DNA40 (which uses a non-linear Ni TCR curve) works pretty well - the temperature rises steadily as you increase the temperature up to about 200C. After this point, based on the TCR profile of Ni200, the mod starts expecting the TCR of the wire to significantly increase (as it does with Ni200). NiFe30 doesn't do this though, so as you start increasing the temp past 200C, NiFe30 suddenly gets hot very quickly.
So you can vape TC in 2 ways:
Method A. Vary the TCR profile as necessary, and vape in the same temp setting range regardless of wire.
Method B. Vary the temp setting range, and vape with the same TCR profile regardless of wire.
With either method, you have one variable and one constant - so I'd argue that neither method is operationally simpler. However, method A preserves fine tuning ability and avoids quirks of mismatches in linearity.
