No I haven't.
Consensus:
Consensus is determined once all participants have formed a mutual agreement and are content with it.
A society can be multicultural, but with a dominant culture prevailing
Multiculturalism on the other hand is...
Collins Definition
Multiculturalism is a situation in which all the different cultural or racial groups in a society have equal rights and opportunities, and none is ignored or regarded as unimportant.
A “melting pot” is a society in which those multiple cultures mix freely, borrow from each other, and gradually blend together.
The two are clearly not the same.
Advocates for multiculturalism would hang you out to dry if you were to state that it's the same as melting pot! multiculturalism is an emphatic rejection of melting pot.
They swear allegiance to the monarch in order to become British citizens, because our monarch is a constitutional monarch, the holder of our unwritten constitution. What they are doing when they swear allegiance to the monarch is not endorsing the monarchy, but swearing allegiance to that constitution.
"Just a bigger idea of with whom to make common cause"
There is no answer to that.
What you are advocating for is a Soviet style suppression of all diversity - religion, race, background - in order that everyone is homogenously British.
It's complete nonsense and it's not multiculturalism.