Hi Jan,
Thanks for pointing out this direction. It is quite enlightening from a scaling perspective, and it also brings out a more fundamental question, not simply DAG or not, but what the appropriate DAG ‘vertex’ should be, be it block, transaction, message, or intent.
I have actually read some of Ren Zhang’s work, and I partially agree that blockDAG approaches likely need further evolution. in particular, they probably should not be interpreted as eliminating the security-performance tradeoff altogether, especially under adversarial or near-physical-limit conditions. That actually is quite relevant in this context.
Reflecting on that, Spora is probably better treated not as a final architecture, but as a research vehicle.
As for a potential upper-layer direction, a true transaction/intent-DAG above L1 seems rather interesting.
As far as I can tell at the moment, Obyte appears closer as a structural reference for a block-free transaction fabric, while IOTA is also useful as a reference for questions around confirmation semantics, tip/frontier selection.
Will definitely explore that line more seriously once this project reaches a stable stage.
P.S. The line of thought touched on here was later crystallised into the CellFabric proposal: