Custom Record Fields

I've hit a couple of walls lately with Custom Record Fields and it got me wondering what's on the roadmap... Can't use constants in Sync Time Evaluation Record Fields - I'm sure this is some sort of backend technical limitation but are there any plans to eventually support them? Can't create relationships with Custom Record Fields (I understand why its not possible with real time custom fields but not sure why they are not supported for sync time). Unable to reference a rule (again I understand the possible performance implications but between this and the 4000 character limit, it doesn't make things easy)