I think the economic and incentive model still needs improvement.

Either I or Ruben (so odds are it's me), don't understand why miners wouldn't have privilege. The users would have to post a multiple, greater than 1, greater than the UTXO that anybody can claim, in order to net out a fee that's much smaller. Eg. User would have to post a fee of 1.01 btc, to claim a UTXO worth 1.00 btc, just to net out actually paying 0.01. Otherwise, the miner would just take the 1.00 btc. Maybe there is something I don't get. Will re-watch/read more.

And, I can't help but notice, spacechain finality will be tightly coupled with Bitcoin's block time. So that axis of innovation (faster finality) feels restricted.