
Archaeik |
I think there's some confusion about the terminology here...
The OP seems to understand the rules, that everything overlaps.
This happens to create a select few situations in which this overlapping simulates stacking.
by default it ends up being whichever bonus is highest
I'd like to be clear that this does not "turn off" the other enchantment the way Bracers of Armor says it does.

mdt |

Note that +10 doesn't actually apply to ammo and bows, or at least, there's nothing in the rules about limiting ammo & ranged weapons to +10 overlapped bonuses. And SKR's FAQ says that +10 is not a hard rule when it comes to powers on ammo (his specific example is a Holy sword with +10 on it total, it's enhancement bonus goes up to +7 with +5 of additional powers vs evil creatures).
So, there's no specific rule saying you can't have a +5 weapon with +5 of bonuses, and a +1 arrow with +9 bonuses on it, and fire them and get a +5 attack with +14 bonuses on it. Other than the god awful expense of doing so.