You text them a link to join the call. The Android user can’t be the one to initiate.
That sounds like a bad joke. "Everyone can use Facetime, except if you're on a certain platform you have to ask someone on the 'real' platform to initiate the call." That's... not a viable communication method.
"Hey there please click on this link to talk to me"
=> Malware! Blocked.
Almost all links I get via SMS are phishing. The rest is OTP, there is sometimes a link in the same SMS but I _never_ clicked a link in an SMS...
My point is, the inhibition to click a link inside an SMS is very high with lots of users, hence I can't imagine this working well.
Also, it's purely inconvenient. You're not having a conf call at a previously agreed time, you want to call someone, this means it's spontaneous or somewhat urgent...