Every brand wants to offer their customers a product that is 'better' than the competition, even if in some cases, 'better' just means unique to that brand.
As a rider i would certainly favour one QR/CL system, maybe even one for 5th lines, one for c-kites and one for SLE's. The actual requirements of each may not be that different, and offering a tool for each job increases the chance of each of them being a success rather than just one that misses the mark for each purpose.
As a company representative it's a much tougher decision, you wear both hats, staff and rider, though 'personally' in an area such as safety i think brand concerns are outweighed by the requirement for the best possible safety system. Though of course my view may not be universal within Best, never mind within other companies.
Just looking at another company as an example, Ozone, i see how their new CL could easily be modified to use our dual-depower line and stopper set-up, as well as the below bar bypass leash. I haven't tried their CL so i have no idea what the QR is like, but it just shows what may be possible.
Certainly it needs push from both sides, company insiders, but also more importantly riders. You guys pay the bills, we design equipment for you to ride, and that's the same for all companies. make your voice heard.
I'd be more than happy to help put together a product brief that defines what is required from a system in terms of functionality, compatibility and phyical look and feel. We do this as a matter of course at Best, all gear has extensive rider input. it's a long process each time but worthwhile.