I am clamoring to see what evidence you have to offer up for Nicholas and Elizabeth beings twins! As of yet, we cannot even verify that Nicholas is related to Matthias. I think that your theory would clarify much, so I am hoping that one day you find supporting evidence.
Elizabeth was indeed married to Walter Hoyt, that's verifiable through tracing the Hoyt lineage as well as a mention of Mother Hoyt in Matthias' will. It's not inconceivable that Walter married twice.
Someone else made mention to me about Elizabeth's middle name having been Susanna. I have not seen it mentioned anywhere, nor have I seen any of the other siblings having has middle names. Really, nothing is known of Richard- I am actually in the process of trying to verify him as an human being. His name is engraved in the monuments at Purley, however, it has been said that this Richard may have not been a Saint John by birth, or named Saint John. More on that when I know something.
Please get some evidence if you can, it's a great scenario!