If the priest is short on time or material - let's face it, some propers offer more than others - then just make it SHORT! I have yet to hear anybody walking out of a church service, particularly an Episcopal Eucharist, saying, "That sermon was just too short!"
Peter's sermon on the day of Pentecost, 521 words including the quotations. Even reading fairly slowly and with expression, it takes less than 4 minutes. And there were thousands of converts!
So my advice as a lay person (albeit one with an M.Div.), "Don't plagiarize. Just abbreviate."