The Rolleiflex Hy6 is an impressive camera and yes I had the opportunity to try one some years ago.
The major problem I see as a working photographer is compared to the Hasselblad and Mamya is the lack of wide angle lenses under 50mm.
As someone who dropped Mamiya 645 system with numerous lenses and now shoot Hy6 with mere two lenses (80/2.8 Xenotar AFD PQS, 50/4 Distagon PQ)... I aint ever stepping back to Mamiya 645 again. Why? The Rolleiflex lenses are much superior and by major margin and the Hy6 is by a very large margin a much superior camera. Among the lenses I owned for Mamiya were two D lenses, the 28mm and 45mm. Do I miss them? No. The 45mm is a good example, tack sharp from corner to corner, but... I found it boring. It lacked character. Each of the current line of Rolleiflex lenses are top notch and with not mere sharpness but a wonderful character. Ok, so Phase/Mamiya have "Schneider" lenses?? Hm... They are not made by Schneider. Only the glass is, and then installed into Mamiya lenses in Japan. Do a search of images shot with the 80/2.8 LS and compare to images shot with Rolleiflex Xenotar 80/2.8. Major difference. Look at the out of focus areas, look at sharpness wide open. Major difference. Why one may ask is Phase One not interested in the best Schneider glass available???
Thus to counter that you ask for wides, I suggest with politeness to ask yourself what you prefer to shoot with (and what is suffice to get the job done); a large variety of focallengths including wide, or lenses that are top notch and with a wonderful character? What will bring you most return on the business? For wider, there is always possibility to add a small tech camera with just one wide lens.
As someone else said there is a 40mm Rolleiflex and with a 645 sized sensor that is pretty wide. From what I understand from DHW they already have a design for a 35mm, however the issue is that it will be very expensive if they fabricate it...
On the camera side, DHW now have the rights to further develop Hy6 on both hardware and firmware side. Those rights are owned by Leaf, a Phase One company. The obvious question one can ask is why does not Phase One invest in the Rolleiflex as a Phase One camera, perhaps an upper line to replace the ancient RZ??? The Hy6 is lightyears ahead in quality, usability and every aspect compared to anything from Mamiya.
Another question is obvious, Phase One have stated they support an open platform system and even demonstrated that in a law suit against Hasselblad on matter the other year. Hmm... one must wonder why they not then offer their own backs for the best medium format camera around, when in fact the legal rights to the system is in the hands of a Phase One company: Leaf.
About Mamiya, I admit I did not like the 645 system, and that I also suffered from several mediocre products/issues. That said, I also had the Mamiya 7 and on the very contrary that indeed was a very splendid and durable system and very well thought out such.