It never seemed to me logical to withhold BMC repair kits while supplying caliper repair kits!
This is quite logical if you think about it. If an overhauled caliper fails you do not lose all the brakes immediately as only that caliper leaks so the other will work at a reduced effectiveness.
However, if a master cylinder repair failed, you could lose all the brakes without warning. Hence the reasoning behind the repair kit supply.
With a front/rear split system like the Murena, if you lost the rear it would probably not be too bad, but the other way around (losing the front) it would often seem like you have no brakes as the front does most of the work! (actually on a Murena with its mid-engine the rears do more work than a front wheel drive car so the rears would be a bit more effective, but lose the front on a front wheel drive car and the rears on their own would give little braking as the harder you push the pedal the more the rear limiter would close the feed to the rear which you need in these circumstances!)
Roy