One of the very interesting and best things about Class D is that those modules can be made modified and made proprietary by engineers.I'm not so sure about it being possible to modify the modules themselves. I believe that they are pretty fixed.
Perhaps the module makers (Hypex, ICE, TI, etc) could tweak the switching frequency for a company like Mytech to impose a house sound, but Class D is high tech and boutique amp makers don't design semi-conductors.
Where the boutique amp makers get to play and differentiate themselves is with the case, power supply, outputs, and possibly a pre amp.