Let's say Austria succeeds in swapping Bavaria for the Hapsburg Netherlands in the War of Bavarian Succession. Given a couple of decades, the Wittelsbach lines die out and the Netherlands, Palatinate, Julich, and Berg come together under the rule of one line - prompting the unification of the realm (Kingdom of Burgundy? Kingdom of Belgium?).
With a unified polity to its North, will France (Royal and Revolutionary) be as inclined towards expanding in that direction?
Perhaps the Prince-Bishopric of Liege might be a target for absorption, especially if it still becomes a revolutionary republic TTL.
Otherwise, given the OTL idea of "lets invade Hapsburg lands for national glory" that occurred during the revolution, maybe Hapsburg Baden could be the target. Maybe Geneva and Neuchatel? More focus on the Ottomans?