I grew up with a Finnish Grandmother in a town with an Apostolic Finnish Lutheran Church. That does relate to preaching themes. The Apostolic Finnish Lutheran Church, which has now dropped Finnish from its name, is a pietist movement formed in Northern Finland and Sweden. It has no seminaries and little formal structure. It uses lay preachers - one, a farmer whom I barely remember, followed by a carpenter/farmer who financed trips back to Finland with "preaching gigs" throughout the world. What did I learn from this. Does the congregation need a preacher? God will provide. Does the preacher need skill in finding a topic? God will provide. Does the topic meet the needs of this particular congregation at this particular time? God will provide. And I built a corollary - if God doesn't provide there is probably something really wrong with the congregation.
So look at a well-known Advent passage in Logos/Verbum:

Now when I read the passage what topics come to mind (remember I trust a lay person's impulse)?
- God's intervention in history
- the Incarnation / kenosis / condensation / God is with us
- compassion (of Joseph for Mary)
- private revelation (Joseph's message from God)
- fulfillment of prophecy
What doesn't come to mind?
- disobedience
- divorce
- salvation
- scripture
- sin
- miracle
That is not to say that I can't shoe them in as topics touched upon in the passage, but it would be dishonoring the actual intent of the passage to treat them as the theme of the passage. Topics and Preaching themes are two distinct things - the first easily identifiable by running a search on books with a type of "Bible concordance" - the latter not actually available in Logos/Verbum as no reasonable analysis of a passage such as Matthew 1:18-25 would find 24 separate themes in the passage. Rather, to offer that many "themes" is to encourage the preacher to ignore the actual contents of the passage entirely.
Some suggestions (short of starting over):