OK, I only have a BX2370, but how far do you have to go before you get separate left and right brakes? They sure can make a job a lot easier. They also can save the day when on the brakes downhill and one wheel decides to spin backwards and the other keeps turning forward. For now I just make sure there is enough rear ballast.
I was just pushing some dirt and couldn't steer and made me think of this question.
I'm gonna go out on a limb here with my "theory" as to why you dont see L/R brakes on SCUTS.
Most of the time in ag fields you wanted to turn around quicker rather than making long sweeping turns to get back to the row you just left - thus separate brakes allowed you to do so. But I am going to bet that most of us - and there are those that do plant with BX tractors - do not need to spin around on a "dime" - the SCUTS will turn fairly quick on their own, short wheelbase etc..
As for separate braking in your situation - would not help at all, matter of fact it would make it worse! As a wheel spins, there is friction - no matter which way is spins, there is a slow drawn out friction inside and outside the drivetrain. ONCE the wheel stops spinning - you are toast, the momentum now is allowed to increase as the friction is no longer! AS the one wheel stops spinning - the other must move twice as fast - thus breaking traction faster! Two wheel locked will increase speed going downhill if traction is lost! Thus the reason all cars now have antilock brakes!
THE best advantage you have when going downhill - especially with HST is to place it into 4WD - even for the manual gears - it would allow ALL four wheel to have braking powers without brakes on the fronts.
Ballast helps - but having all four wheels engaged is the best way period to have control on the ol "slippery slope"