It's certainly not standard to use phrases like "we are hypocrites" to mean "I (royalty) am a hypocrite". Quite simply, in English (as well as in French), the "honorific" type of "plural" pronouns do not automatically trigger plural reference for all other references to the person. There is really no such thing as true "agreement" of a lexical noun with another word in English. Nouns are pluralized when it is semantically appropriate to do so; they aren't pluralized just because of the existence of another plural word in the same sentence that is grammatically related.

 "We" can mean "I", but "hypocrites" cannot mean "hypocrite". There are many ways in which pronouns don't behave the same as nouns.

Margaret Thatcher infamously said 

> [We have become a grandmother][1]

after the birth of her grandson. Note that this is not "we have become grandmothers".

(Of course, Margaret Thatcher is not royalty.) I couldn't find an example of an actual sentence of this exact type spoken or written by a historical English monarch, but here is an excerpt from one of Elizabeth I's letters that shows the general pattern of use:

>...to be imployed bothe abowte **our owne parson** and otherwise, as they shall have knowledge geven unto them, the nomber of which larger proportion as sone as you shall knowe, wee requier you to signifie to our privie Counsell, heerunto as wee doubte not but by your good indevoures, they wilbe the rather conformable, So allso wee assure **ourselves**, that Almightie God will so blesse their loyall hartes boren towardes **us their lovinge Soveraigne** and their naturall Countrie, that all the attemptes of any ennymies whatesoever shalbe made voied and frustrate, to their confusion, your comfortes, and to Godes highe glorie.

(http://www.luminarium.org/renlit/elizinvasion.htm)

I bolded the parts I think are relevant. Pronouns are consistently plural: "we", "our", "ourselves" (although in other texts, "ourself" can be found). But the associated nouns are singular: *our own person* (not "our own persons") and *us their loving Sovereign* (not "us their loving Sovereigns").

  [1]: https://www.youtube.com/watch?v=s5Gxruh-pLI