I'm sure the writers could come up with a reason for T'Pol to turn up. Like the hypothetical scene with Sarek quoted earlier.
R. Wilson's casting didn't happen until they had already started shooting the second episode, so Harry Mudd isn't the answer since he won't be in the 1st or 2nd episodes for certain.
Of the alternatives proposed so far (including my own) I'd go with Tenacity's suggestion of Dax. The fans would appreciate it and there is no baggage.
If you want someone from Enterprise, T'Pol would make sense. She'd be around 160 years old, and we know from E² she was alive at 183.
You're assuming that they announce casting as they happen. We know that at least in the case of Sonequa Martin Green, this wasn't the case. It's very possible they delayed announcing Rainn Wilson, as well.
The looks suspiciously like another thread...started by me. It has much better suggestions. https://www.trekbbs.com/threads/pilot-episode-cameo.286365/