it has been reported on the Loksound forum on groups.io that the treble and bass adjustments work on v5 decoders when the decoder firmware is updated. I would expect the aux functions to already be available, remember this may not be for H0 and smaller decoders, but rather for the larger scale ones.

But I come back to what I thought when I first heard that Marklin were doing 16 functions on the mfx decoder - what would you use them all for? At the moment we have a lot of sound functions that really only get fitted because of the number of logical functions available. So what would one REALLY do with 18 physical functions???

ESU Loksound 5 do have 31 functions. ESU do also have more AUX functions than Märklin. I am pretty sure that more output functions will also be held for the scale H0. Time will see what locomotives do have possible fits more output functions.

In the Marklin msd3/mld3 decoder, if I understand it correctly, the configuration files go up to 20 physical functions (up to PhysicAux18 + lights) and 64 functions. (and 80 mapping slots). This has been in the files for some years, but I guess is just some future proofing from Märklin.........?
As a side note, Flying Scotsman uses 12 physical functions, with 7 on SUSI (If have counted correctly).

What I do wish for is a more updated decoder from Märklin with more physical aux functions, but within the capacity of the MTC 21 connector, with a choice to use the pins as aux or sensors/motor3) Or perhaps a decoder plate with built-in Susi outputs.
On some of my conversions, I have run out of physical aux, but 2 or 4 more would have been nice. (yes I could have used a different brand, but I managed with some small compromises). E.g when using the 60973, which requires 2 aux to work, you quickly run out of physical aux.

So I hope this news from ESU will force Marklin to act ;)

I also like good sound, but it's hard to improve the sound from locomotives, as small speakers are the limit.
It will be interesting to see if Mems speakers find their way into model railroads. But currently, they lack performance in the lower tones. but they have made speakers with them, but they have conventional bas elements.

That probably depends on the maker and model, but it seems like some are: xmems.com, https://spectrum.ieee.org/mems-speakers