I see no reason to change the 5 basic patterns.
I just came across this thread today. I found it interesting because I've written a grammar that puts a great deal of emphasis on sentence patterns. It's posted at
http://www.ColorCodedEnglish.com. Some readers might also find it interesting that a standard reference book for English composition,
The Harbrace College Handbook lists six sentence patterns.
After a couple of years analyzing sentences, I also concluded that the five traditional patterns did not account for all English sentence structures. However, my solution was to redefine the five patterns based on verb complements.
I recognize five verb complements: objects, predicate adverbs, predicate nouns, predicate adjectives, and predicate verbals. I actually coined the term "predicate verbal". Most grammars view them as predicates of non-finite clauses and their non-finite clauses as objects. According to transformational generative grammar, the following two sentences have the same pattern.
"She wants him to sing". / "She said he should sing". / S - V - O
The concept of "predicate adverbs", however, is accepted by many linguists and grammarians. These adverbs are complements as opposed to adjuncts. Grammars that recognize the term "predicate adverb" would disagree with the view that the adverbs "upstairs", "in London", "on the table", and "to my friend" are adjuncts in the following sentences.
"He's upstairs" / "She lives in London" / "Put the book on the table" / "I gave the money to my friend".
Distinguishing predicate adverbs from adjuncts, however, can sometimes be quite difficult. It's not a practical concept for basic grammar instruction, but it's useful for analyzing sentence patterns. Predicate adverbs of linking verbs are components of the sixth pattern in the Harbrace Handbook.
I believe that "subject complements" share the same function as predicate adverbs. They all complete the meaning of the verb. The meaning of the subject is merely modified by subject complements. It's a misleading term.