Without being able to enforce a timeout on the exploding path, I don’t think having a key path is very interesting? In adversarial scenarios you can’t use it, because your adversary can just broadcast the exploding version; in non-adversarial scenarios you wait until feerates are load and use the key path to spend directly to wherever you want and don’t need an exploding tx in the middle?
I think you could extend this design to fix that, though, by making the commitment something like:
keyZ = H(nLockTime, nSequence, annex)*G
keyW = KeyAgg(keyA', keyB', keyC', keyZ)
with nLockTime, nSequence and annex pulled from the exploding spend. At that point, A,B,C have until the locktime/nseq expires to agree on and broadcast a key path spend, or after that time, they all just get their money back via the exploding tx. That would allow a one-shot payment pool, I think?
I don’t see a way to tweak the maths to allow you to have both an exploding spend path and a script spend path – I think in that case the exploding path would still need to reveal the script (hash), and at that point you might as well just use a script path in first place?