This is the setup I run also. The limitation I run into is that I am unable to switch the "leader" if my main dies or would like to switch for any reason. This is why I'm praying for an /assist master function for Jamba to replace /assist party1 or /assist main. It would solve all my problems.
..well its basicly the same idea you run. But frosty runs it in an ftl-way and you on an focus-based-jamba-way i thinks, so not exactly the same, as your problem is not a problem with the ftl approach, because in an ftl-setup there is no constant 'leader'. Also I must admit an /assist master would be nice for jamab, but I think not doable, because macros and targeting can't be changed in combat by an addon.