Qexl, thank you for your constant support and spot-on response. For all that I don't always find time to get back, I always appreciate and I'm grateful for the time you take to do such a service to this community. You might consider yourself as an old person but let me say, it doesn't look so. Your reasoning is refreshing. Yes, it is crystal clear by now that any sound coming from Pianoteq has some kind of magic which can't be denied. I totally agree and you did good at stating what has to be stated.
The piano can make you cry out of joy. Sometimes, I cannot believe the level of perfection that has been reached. On the other side, there is another reality that I find interesting as well. You will always find a bunch of people concerned with this and that, about how 'the piano' doesn't sound realistic (the highs are piercing, the mids are muddy, the touch feels bla bla bla). Or even more, which speakers do justice to Pianoteq, and all the rest. Ok, I get it, all this must be true to some extent, right? But, at the end of the day, it is simply impossible to please every single listener (I also doubt they would say what they say if hearing Pianoteq in a mix or in blind test conditions). The company has a lot to do - let's not forget they also launched an iPad version - and yet I'm confident they will do the impossible to satisfy every single customer no matter what.
I'm still learning 1%. A simple piano preset in Pianoteq can change dramatically its own quality even with the slightest tweak of microphone / binaural configurations, with parameters like stereo width and sound speed. So whenever I say 'sound design', beware! Because I don't know what I'm saying. All I know is, if the sound source already sounds good and comes directly from one device only as well, then adding more audio processing literally makes no sense. Most of the time, the operation will destroy the magic and compose 'noise'. Same goes with putting reverb like salt. There is no ultimate solution. Even adding another valuable sound material, a new voice or whatever, is often enough to ruin a moment of magic... and that moment in music should remind the listener of eternity, not clichés.
Now I don't want to go off-topic with philosophy, let alone personal taste, and I also live by the hope, as you aptly said, that "Pianoteq continues to do what they find is fun, as much as continue bringing beautiful pianos to their wonderful library". So what I had in mind with the classic 'synth-like' question basically reduces itself to the paradox of not embracing 'synth-like' trends and rebuking 'new-age spectralism' such as modal synthesis at the same time (as there are many plug-ins trending in this field).
I don't know if I'm explaining it correctly, it's nothing revolutionary really. I just expect little ideas (such as hooking some behavior of the Note Effects to 'note-offs' as you suggested) to continue to be hidden gems, so to say. In short, details which could make the difference rather than details onto which whole instrument packs get designed. Then anyone can design anything with and without 'morphing'. That's it. I'm no audio technician either, I like noises, feedbacks and the freedom in art. Only I feel like I belong to a niche that secretly refuses to comply to loudness war standards. You know, modal synthesis can become just as loud and standard and I don't care a brass farting. People decide if what's on air today is noise or something else. Sure thing is making music by digital means has actually become so funny and easily accessible, that apparently only people with a certain experience (old?) understand all the possibilities behind the technology... you name it, 'secret sauces', and to each their own ;)
So yeah, this Modartt product is so impressive that I think other paid softwares are not worth to be mentioned in the discussion. Different would be if we were speaking about free formulas for physical modelling or open-source projects like Csound (see the outstanding physical modelling developed by Iain McCurdy), but this is also not the case. Back to Pianoteq, you provided an excellent description regarding the current "Note Effects" possibilities and the hypothetical future ones. That was a fundamental piece of information I forgot to give to the readers (to be honest I even forgot that the wave shapes could be changed before making the post).
Regarding #2, maybe I used a wrong expression instead of 'glissati' or 'glissandi'?
By monophonic / polyphonic portamento, I intend that the note(s) glide(s) within a certain time span and depending on some curve (otherwise linearly). The monophonic version is so well-known, that is found on most monophonic synths (analog or digital) and step sequencers, but the polyphonic is not so common. I own a couple of hardware synths that have implemented the latter, Waldorf Kyra and Korg Prologue. It sounds different when those two are layered, but the overall effect of their respective polyphonic portamento is very exciting (especially when you add, on top of it, the fact that both synths support 1 cent precision scale modifications).
Anyway, the velocity or rather 'pressure' on the key altering the pitch like you said is also a good idea! It happens to a certain degree with real pipe organs (I'm ignoring if Organteq simulates this). This is used as a compositional technique in the Harmonies etudes of Ligeti. But 'polyphonic portamento' is not necessarily so subtle and hard to control as each note can glide independently huge distances as well, from the lowest to the highest register (or the other way around).
So monophonic glide I would say expresses itself as a classic 'synth-like' function but polyphonic portamento is not that avant-garde really (since there are examples of modern synths exhibiting it already, like I said, in slightly different fashions). It resembles to 'pitch-shifting' - only it's not global, but per note. It also resembles to 'dynamic microtuning' in the perceptual sense - but the scale doesn't change. Definitions are always tricky, sorry. However, any polyphonic portamento/glide is 'a posteriori' to any temperament application, and, by definition, it must tend to - and eventually arrive at - the same scale, because polyphonic portamento doesn't change the scale steps at all. All it does is filling the voids between the same scale step frequencies.
If the time span during which the voids are filled is not too short nor too long, the result then will be a bit like what 'meend' is to Indian music. The complexity brought by the fact that there are not just two notes of a single melodic line but potentially different chords and voicings, can be faced in many ways by setting some 'note priority' (a story which Modartt can figure out in the blink of an eye).
To be fair and to conclude, I'm aware that polyphony, and polyphonic gliding voices thereof, are a complete heresy with respects to Indian classical music, and I can't hide the fact that 'progressions' can sound messy when they are not pretty handled. I just think that, at least from a theoretical point of view, different new proposals are to be shared also as far as the "Spectrum Profile" per-note exploration can go with Pianoteq.
Will we be the only two persons in the world to drop a few lines thinking about it once again? Bizarre!