You could split this map in two, using the streets at the top as a smaller street battle map and the bottom half as a market place battle map.
NPCs can run out of buildings to enter combat.
Some of the stalls are rather nondescript, so you can add in your own story based merchants.
The grey/blue tiled buildings towards to top left could be a tavern with small stables in the back.
The connection between the two large market square buildings has an arch under it leading to the rear of the building and the street beyond. This could be blocked by a door that opens during the encounter to reveal more combatants.
Place doors to buildings to help with your particular scenario.