Tbh that doesn't really work for me because it would change Zhao Yunlan in such a fundamental way

Depending on what kind of a father he was, and how long he'd been parenting. If he hadn't actually lived with the child (or even necessarily known about them) until just before canon starts, it would be a complication, but he'd still be himself. But anyway, don't apologise. And it's well down my list of things I've considered working on. :-)