Thanks for starting this thread Kradia!
I definitely would welcome a change like this. Not necessarily because it might help bowmen, but because one of my earliest memories of playing Maplestory is earning my first few mesos by crafting regular arrows and selling them just below npc value (I was a 10-year-old capitalist I guess). If arrows that give attack value were easily craftable and not useless for bowmen, it could be a fun way for new players to earn some cash.
The suggested change to Soul Arrow seems good. I always assumed the skill used the attack power of equipped arrows until I found out it doesn't, which is just bad Nexon design if you ask me. We may want to test the duration of the skill vs the amount of arrows consumed in Tespia to optimize it.
As far as buffing bowmen goes, we are clearly a disadvantaged class. In comparison to hermits for example, we have less ability to make mesos, less survivability, and less damage. However, there's plenty of bowman players, so I don't think we need huge buffs. I do think this Soul Arrow change might be quite difficult to code, at least more difficult than the other suggested bowman changes, which I think should be prioritized if any changes are made: