Poor Fritz

 Dynaudio and others were doing this for years with Totem and other manufacturers starting out with custom quality wound voice coils, better magnets, or surrounds, and different baskets in special circumstances

Why arent these supposedly better versions already being produced and offered for sale to the public then? 

Because the DIY public doesn't keep their doors open the large scale manufactures do.

+1

Some people look at a speaker from a photo and make assumptions on parts and materials used inside, and the manufacturer total cost for each component used. It’s not always comparable in function, sound, or cost just because it looks the same from the outside.  

From my knowledge, Fritz does not use modified drivers.  What he does have is great knowledge of the different drivers.  He stays up to date with any revisions made to drivers as well. He memorizes the weights of the cones and which drivers use what drive systems.  He understands that Seas Excel Drivers, while being great, and drivers he has and will use, actually ring above a certain frequency.  In order to overcome that ringing, you need to make a more complicated crossover.  Fritz likes to use the highest quality drivers and keep his crossovers as simple as possible.  
Fritz is a speaker chef.  He knows what ingredients to put together in order to create delicious dishes.  The ingredients are the drivers he pairs together, the seasoning is his crossovers, the dish is his speakers as a whole.  His house sound, to me at least, is like those vintage speakers in their warmth, tone and fullness, combined with the accuracy, imaging, detail (sparkle and shimmering- Carreras) and accuracy of a thoroughly modern speaker.   

Some things in life are more special than the sum of their parts.  Fritz’s speakers are one of those things.  His Carreras are awesome and if you are on the fence, just get a pair already.  Im sitting here listening to them right now and I promise you, you would love what I’m hearing.  I’ve spent hundreds of hours listening to good sound at Audio Shows so I have some frame of reference.  Fritz knows how to build a high quality, fun to listen to, rock the house monitor speaker at a cost that I don’t think can be matched except for a few rare others (tekton, salk, etc).

OK, since no one will read the actual definition, comparable is not EQUAL IN ALL WAYS.

For instance, a VW Tiguan is comparable to a Subaru Forrester.

And yet again, people are nit picking the poor man's great value speakers in ways they would not for a famous badge.