[=;223127]
Hey Eric,
I just attempted to upgrade another copy from 4.6.1 to 4.7p7 so I could send it your way and noticed something I missed first around. If I try to save my level in 4.7 I get a total of 21 warnings on MapCheck for BP_Skydome(11 warnings), BP_Ocean(2 warnings), and each of MaterialInstanceDynamic (total of 8 warnings) variables for both materials saying they are “Externally Referenced”. From look of it I would say you described above fits pretty well, setting a non-editable variable.
If you guys need a copy of it for any reason just let me know as I can easily provide a link now, but I’m pretty confident (99% as well) that we are talking about same here. Thanks! 
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That has been fixed. There were some backwards compatibility issues with components in blueprints not being publically exposed.