This morning I got an idea for Minsc to dual-wield and have bow equipped in my current BG:EE run and it worked. I edited Stupefier so it would create undroppable composite long bow +1 and off-hand mace +1 on equipping. When I put arrows into slots, the bow activates (it is edited to remove the off-hand mace on equipping) and then, I can switch between those in quickbar. You can remove the bow by activating its special ability in the item slots. One disadvantage is that you must click on the bow twice on the quickbar, or the swing animation remains that of a mace (it won't break anything though). I will try to fix that somehow. Important: Make sure to clear all weapon slots and shield slot before equipping and equip Stupefier *in the first weapon slot* (the bow is created in the second slot).
To install, extract the rar below and put the three files in the override.