And just to make it clear: The only simple fix I see is to remove all variability for to-hit and to-damage from all missiles. If you want that please file a separate RFE. Personally I do not like the idea too much.
Well, I'd say yes to that. I already assumed the fix for p21 would concern all missiles, and I thought it was brilliant. Disappointed it was not so. The issue is, if someone's using archery often, and has autopickup missiles on, there will be oh so much rubbish in the inventory with single arrows with different to-hit, different damage, different status and prefixes... And they are basically unusable, because having to reload after one shot is tedious and dangerous. Having base to-hit and damage the same would make less rubbish and more meaningful stacks.
And on the flip side - +3/-3 differences in to-hit/damage aren't all meaningful. I think we can live without them. And actually prefixed missiles could matter more.
I have posted not long ago solution without modyfying to-hit/dmg bonuses of missiles. {3956}
But implementing this rfe require little programming.
Please check this out :)