The two examples you presented are actually pretty historically accurate. The influx of European troops into the Holy Land is one of the main reasons the Crusader States were even able to survive for as long as they did and were a key factor in keeping the territories conquered by the original Crusader armies.
While Crusader States were independent governments, and they often formed alliances with Muslim forces, as far as I know, they never warred with one another. There was much more political tension and rivalry between the Crusader states than there was outright fighting between them.