Really productive design session today. We were able to re-contextualize the alpha in a much broader, more global view. Basically the gist is that a unit is the most atomic part of the system, and can contain child units, chats, and so on. The overall structure is a recursive list of units.
We are also playing around with adding a third dimension, that is, the exploreability/solidity dichotomy. As branches of a discussion are expanded out, they become more solidified and thus are more visible at a coarse-grained resolution. Less explored directions are visible only at a higher resolution. Discussion branches out in a hierarchy of multiple dimensions, both in terms of topic/category, and potential for future exploration. I like this direction in that besides solving a number of key questions we've been asking, it balances the conceptual/future state with the concrete/present state.
Lots of specifics to continue to hammer out to see what implications this design has for large 500+ person groups and small, more intimate 2-5 person ones. But the key is that on paper at least the same structure should apply to both.