Of course what we really need are solid state detectors for our WDS spectrometers!
I am completely not sure about that. Why? (1) it probably could be ok replacement for low pressure counters; However providing very stable cooling of such detector is very challenging. We probably could use cooled nitrogen and same capillary to transport heat from the SDD. To cool SDD means there should be enough pressure of nitrogen, or lower pressure nitrogen but cooled to some low temperatures (then lots of liquid nitrogen is required). SDD and its counting electronics drift depends from temperature and humidity (We need to calibrate EDS SDD on SEM much more often than on EPMA, as the air conditioning is less sophisticated there, and SEM experiences more temperature swings (the SDD itself is cooled at stable set temperature, the decalibration is clearly a response to temperature and humidity variations by pulse counter unit (EDS SDD electronics))). This is why I am also not 100% sure that PHA drifts are directly produced alone only due to atmospheric changes, and rather suspect that electronics react to atmospheric changes too, in particularly that EPMA shaping and counting electronics is much less sophisticated from EDS pulse processing units, and low pressure counters most often works at lower BIAS and much higher GAIN (which means that gain-OPAMPs can swing the signal much more, than on high-pressure low gain spectrometers).
Partly problem with low pressure counters are the PHA drift. But if You use integral mode, there is no problem, as You still are counting same amount of counts (the counter bias can be set higher or lower in some margins which does influence pulse height, but not so pulse density).
SDD can look as that nice stuff, but there are many artefacts which would influence measurement linearity in particularly at low energies and is very hard to resolve:
incomplete-charge - no such thing on proportional counter
Si esc peaks - on proportional counter we have Ar esc, but for low energies it is not applicable.
Generally new design of proportional counter electronics could solve most of proportional counter problems (PHA resolution, pile-ups, increase linear throughput, intelligent bias offset depending from room temperature), while there would be no need to hardware changes inside spectrometer.
Actually there is no obstacle to use the last one NOW. Stick some digital thermobarometer (hygrometer) in the room. Log the values, apply some low-pass filter. Make correlation curves between bias and environment. Add some code to PfS to adjust bias depending from room environment -> profit.