I wouldn't say it's unappetizing for us. Even contemplating the possibility offers us insight about what companies the size and complexity of Stripe need to go through in order to migrate Billing systems. e.g. back of house processes for revenue reconciliation and recognition need to work across both systems, we need to support bulk migrations of data, both systems need to recognize the "canonical biller" for a customer so that you avoid double-billing issues, you need to backfill invoices and ensure no gaps in numbering, product teams need to update their integration and provisioning code and so on. My observation is that large companies can spend 10s-100s of engineers on the order of several quarters or years to do this kind of migration safely.

We've made several internal and a few external changes over the years to help our users with these kinds of issues and in my estimation we've been getting closer to making the commitment, but as of right now we haven't done a stop-the-world effort to change systems internally.