Modding matchlock range?

Reading Stephen Turnbull's book on the Japanese invasion of Korea (the long one not the Osprey booklet) and one passage on the battle of Sangju struck me:

'The death of the scout confirmed the presence of the Japanese. Fierce arquebus fire then followed, which begun to cut into the Korean front line. At this Yi Li ordered his men to return fire with their bows but the arrows fell short ofthe targets' (p.58).

Earlier Turnbull has already pointed put that the Korean composite recurved reflex bow was effective up to 500 yards and thus far superior to the simpler Japanese laminated longbows which had a range of 350 yards (p.20).

While somewhat dubious about these ranges his source is an un-named contemporary Japanese account which means that Japanese bows were indeed believed to be inferior in range to the Koreans by those who'd actually seen them in action - but that at Sangju Korean bows were outranged by Japanese arquebuses.

Of course neither bows or arquebuses had much chance of hitting what they aimed at at 500 yards (although Japanese teppo were arguably more accurate than eighteenth century muskets like the Brown Bess as they actually had sights - which nobody in C18 Europe thought were worth using on military weapons as reloading speed and the morale effect of maintaining disciplined volley fire was more important than accuracy) but there were good reasons that late Sengoku era Japanese armies like C16 English armies quickly employed many more arquebusiers than archers.

Something that has always annoyed me in STW2 (and even more so in M2TW) is the uselessness of matchlock units in field battles (at least in legendary SP where you can't stop or slow down the action to micromanage them so they avoid being slaughtered in melee or by archery) - although in siege defences where they can stand safely behind walls they are my champion killers.

Just upping the matchlock's range would be profoundly unbalancing so what I had in mind was giving the matchlocks equal range to bow monks but reducing their accuracy.

So how do I do this with the minimum effort? - I used to mod M2TW and RTW but have never touched STW2 or NTW and am thus a complete noob.