Or (bluntly): why not Matrix (and/or XMPP)? What makes WA so much better that you're willing to go all-in with this company?
I'm not taking anyone with me, they already have Signal and WA and obviously SMS. I'm uninstalling Signal and not recommending it again. I can already message Signal contacts using WA or SMS. I don't need Signal for that, and I'm not keeping 3rd messaging app.
now give me Matrix client with basic SMS support (I don't need even MMS) and I'm installing it immediately to replace my dedicated SMS app
I did same love with family as poster, from Signal with family, WhatsApp and SMS just to WhatsApp/SMS combo though already years ago after PIN nagging