One candidate for a second MF system is a Pentax 67 slr.
While the Hasselblad V with various viewfinders is very versatile, I've noted that a number of Hasselblad owners own the heavy Pentax and lenses, often using them in the field, for, ie Racing and Sailing imaging, street shots, and rugged terrain environments.
The first MF SLR system I ever saw was a Pentax 67 on the island of Eniwetok, in the hands of an experienced officer, making pics of Typhoon Alice's destruction and the effects of a still strong winds environment.
With my 500cm I could make good shots as well as the Pentax, probably better, but I'd rather have the choice of the Pentax, as it was a very tough walk-around and the heavy weight of the Pentax in a tripod would be a benefit, rather than what I'd normally consider a negative.
One more example is mass transit, bus, trams, street cars, trains, boats and planes.
I'd much rather use my TLR cameras, a Sawyers mk.IV 4x4cm or my Minolta Autocord 6x6cm on these venues than. Hasselblad simply because of the more simple appearance that generally does not peak much in trance and some folks are happy to see these in use, as their Dad, Mom, Uncle, etc had one that they used and it brings up fond memories.
Diana's, Brownies, Ansco 75, etc, more style considered "toy cameras" also have a place in Hasselblad owners kit, and practical and creative photographers, also use pinhole cameras.
It just depends on the person involved how far they are are push their creative passions or prepair for 'Business' needs.
Cheers.