When Malcolm Newell and Ken Newman first brought ut the Quasar FF I thought it was a brilliant idea but could never understand why they used the Reliant engine and gearbox, it just seemed to make it unnecessarily complicated. surely there must have been a bike engine that was better suited?, like this
https://www.ebay.co.uk/itm/256051998053 ... SwffVkSXdp
If I had the money and the ability I would love to finish this off. Some Quasars had brilliant paint jobs and looked the business, having said that I've sat on the one at the motorbike museum near Birmingham and it would take a bit of getting used to.
On the minus side that's two less GTS's on the road.

In many ways hub centre steering was a solution looking for a problem and once ordinary telescopic forks and disk brakes became better engineered the companies and people that tried it, both for racing and road machines, never proved that it had significant advantages. Even the likes of BMW dropped alternative front end designs after trying them on a few models. As for the power unit at the time there were only Japanese alternatives if you wanted a multi-cylinder water cooled design hence the quirky choice.

Your right about centre hub steering over the years it's appeared and disapeared again several times, though people who've ridden them tend to say they like them that may have more to do with the leading link suspension they have.
It seems the Quasar came in many configurations with various engines, GS 850 and 1000, Z1300 and VF750. The 750 Reliant was a good engine in many ways it was the gearbox that was a problem in the Quasar.
I came across this video of one in action in New Zealand.
https://www.youtube.com/watch?v=MV4qVbNPX_w