There’s a relevant question regarding lightning network payments:
I have five $2 channels, is it possible for me to atomically send $6 to fulfill a payment?
this might be rephrased for the safe network as
I have five $2 safecoins, is it possible for me to atomically send $6 to fulfill a payment?
The lightning network has a proposed solution called Atomic Multi-path Payments.
The main benefit is “adding a strong guarantee that the receiver won’t be paid until all partial payment flows are extended.” The sender will “deliver additive shares of a base preimage, from which the payment preimages of partial payments can be derived. The receiver can only construct this value after having received all of the partial payments, satisfying the atomicity constraint.”
Even though it operates on quite a complex / different structure to safecoin payments it’s something I think is worth at least being aware of since it has a lot of similarity to the problem of atomic safecoin payments.