Great writeup! I've been using `jj parallelize` [1] a lot (and wrote about it here [2]) to fan out a sequence of commits to set up a megamerge, but your stack alias sounds super useful to create them on the fly, rather than at the very end of a work stream. Thanks for the tips!
I imagine it will be really hard to compete with completely free alternatives like FreeSign[1]. Have you considered giving a free tier, or at least a free trial of sorts so potential subscribers can test the flow?
[1] https://docs.jj-vcs.dev/latest/cli-reference/#jj-parallelize [2] https://blog.chay.dev/parallelized-commits