Is this example correct? (omitting subject in compound sentence)
Solution 1:
The bare bones of your sentence are:
Morneau | will have been acting and shows
It is not a compound sentence, i.e., with two independent clauses, but a simple sentence with one subject and a compound verb joined by and. By the rules of traditional grammar, the comma should not be there. Or you may add the pronoun he to produce the second independent clause, as your friend suggests, but doing so merely to satisfy a comma rule doesn’t seem especially satisfactory either: there is no ambiguity as to who the subject of shows is. So why bother?
The other suggestions are merely stylistic, but still don’t deal with the comma problem. Adding a contrastive, either and yet or just yet as a conjunction, changes the meaning of the sentence. Sticking in two years time at the end of the clause merely makes the future perfect sound clumsy, so it’s hardly an improvement.
In longer sentences,however, especially as here where the verbs are different tenses, even the best writers toss in a comma. The best solution, then, would be either toss the comma or leave the sentence as is.