In Waterdeep: Dragon Heist, there is an encounter that requires a large number of similar NPCs/monsters, based on the (slightly edited for spoilers) text block:
the City Guard arrives and cordons off the Alley, posting six guards at each entrance. The guards don’t allow anyone in or out without permission from a superior officer. Another six guards, including a sergeant with 18 hit points, make their way to the crime scene and watch over the scene until the City Watch arrives.
The stat block for guard has a single action as a spear.
However, presumably a squad of this size would have a mixture of weapons for different situations, ranges, damage types. So instead of 12 City Guards armed with spears, I have 4 armed with spears, 4 with maces and 4 with shortswords and changed the to hit modifier and damage to match the RAW attack and damage values for Guard, so if any combat starts, there should be no statistical difference (apart from vulnerability/resistance/immunity damage types).
Are there any unforeseen issues with changing the weapons like this? Are there better/recommended ways to make these changes?