I agree, relighting is tricky, not just because of the limitations that you describe, but because there is a lot less cumulative experience with relighting of e

I agree, relighting is tricky, not just because of the limitations that you describe, but because there is a lot less cumulative experience with relighting of engines than simply lighting them at the launch. We (as the entire humanity) have seen tens of thousands of rocket motors lit on ascent, orders of magnitude than those relit. Raptors don't seem to be prone to kabooms during flight, probably because the command unit switches them off in case of any suspicion.