Craonne (the game) converts easily to vassal, with a small map and a few-dozen units per side. The map graphics in the four-game Sandhurst Wargames are quite artistic and evocative; the counters less so, but they're fine when scanned for use as vassal game-piece images.

The design of Craonne is slightly more complex than SPI's Napoleon at Waterloo. The system features indecisive combats that can end up with both sides "pinned" until reinforcements arrive or someone disengages. Fresh units can tip the balance in these situations, so having a fresh reserve and commiting it at the right time and place is part of planning. There are a few rules holes, but nothing serious. For more information, here's a good review and after-action report from grognard.com

Link to Craonne vassal module.

Contact me if you need a PDF copy of the rules and tables.