Summary: This is a case where the Greek does not alter the meaning, but simply forces us to slow down and examine Jesus' familiar words. Jesus offers a strident critique of an overly consuming, self-aggrandizing and elitist clergy. Yikes. More generally, I think Jesus makes a comment on how all of us consume and how we give.
βλεπω (12:38; "see") The word here for "watch out" is simply the Greek 101 for see; Jesus will tell his followers to "watch out" five times in this section (12:38, 13:5; 9; 23; 33).
γραμματευς (12:38; "scribes") This word has an obvious English cognate: "Grammar." The question for us today is, whom do we need to watch out for -- who are the grammarians today? I struggle with this question a bit more personally -- how do I become a grammarian, who says "no" to the working of the Lord, either in my congregation or in my denomination? How do I NOT become someone whom Jesus warns against. The further description of Jesus' critique includes:
they wear στολη (12:38, "stole" or "robe")
and sit in the
προτοκαθεδρια (12:39, "first seat"). Ouch.
κατεσθιω (12:40, "devour") As you guessed, the Bible uses this word in an entirely negative fashion. It also comes up in the prodigal son, where the son has consumed the father's property (literally, βιος, used also in this passage in vs. 44). One can read this passage as a narrow critique of 1st century Jewish leadership, more broadly of religious leaders over time, or most broadly, against all over-consumption. In what ways does our whole culture "devour widows houses while praying long prayers." A prophetic voice is helpful and perhaps here, but how can this be done so that its not simply an attack on others (or in an election year, people who voted differently), but a call for all of us to repent?
βιος (12:44, "life" The woman gives "the whole of her life" The word life here is "bios." So the sermon is not about stewardship of money, but stewardship of everything.
Grammar note: Here we have a substantive participle "the ones who devour" followed by a participle "praying." There are a couple of ways these two participles (devouring and praying) could be related. I think the best way to translate the participle "praying" is as a circumstantial participle: "the ones who devour widows houses while praying long prayers." Ouch! They pray while they sin.