What amps have you removed the output filters from so you can test your "idea"? What amps have you raised the switching frequency on so you can again....test your "idea"? You have interesting ideas. That is all they are. You have no proof. More and more people everyday are listening to 500K switching amps using mosfets and they do not hear the "terrible mids and highs" you keep talking about.
On the other hand, I agree with you about switching at higher frequencies being a "possible" positive (apparently hard to do without drawbacks....Merrill even says so). You could make the coil smaller and it would have less effect. As far as dead time there are various ways of dealing with it. Everything will be known about all this within 10 years. In the mean time we have great sounding relatively modest costing mosfet based amps that are replacing class A and A/B amps all over the world. Not that any class D amp (including the new Merrill GaN amps) is state of the art. I am sure the $100,000 plus Class A amps are still the best there is (Audionet Heisenberg, DAgostino Relentless, etc.).
I really hope that GaN transistors can help class D get even better. However, there is no proof yet. Even the $36,000 Merrill GaN amps don't do depth or dynamics or classical music as well as the CH Precision stuff (according to one guy who had them both in his house). Most of the class D amps out there are inexpensive, use off the shelf modules (including mine), are not being produced by serious tweakers, etc. and therefore are compromised. I do 17 mods to the modules and hook them up in state of the art ways and sell wholesale direct. This is why my amp is so good for the money. It is not state of the art.....no way. State of the art means the best available period.....Heck, that bar keeps changing every year....even at the $100K price range. Class D is very good right now and will keep getting better and better at cheaper and cheaper prices. If GaNs can help this trend then all is a WIN! I have high hope for GaNs...let us see what happens. Right now there are no (zip, zero, nada) tweaked out affordable GaN amps available (the inexpensive Technics is not a tweak product!!!). This is going to take some time. What is for sure (and I keep saying this over and over....so here goes again)......is that every amp with GaNs (when and if they get released) will sound different from every other amp with GaNs or whatever. Every single thing you do changes the sound. Unless you invest tons of time tweaking something you will never get what is possible. I have been tweaking the IceEdge modules for a year now and am just now starting to ship. Perfecting and tweaking takes time. You will have GaN amps that do not sound as good as mosfet amps.....that I am sure of. There is no silver bullet. Everything has to be done right. I hope that GaNs done right are another level better....I always want everything/everyone to improve. I want everyone to feel happier and happier with each day. May it be so.