I plan to make a multiclass character with a Rogue and a Ranger. Since I want to stay at a distance when attacking, I want to use a shortbow (with the proficiency from Rogue), but I also want to use a shield (with the proficiency from Ranger). This is not possible because the shield takes one hand, and the bow two.
I want to make a custom weapon, combining a shield with a bow, like a bow attached to the shield (so my character is holding the shield/bow in one hand, and shooting the arrow with the other) My DM would allow the construction of such item, but I want to know what kind of interaction this will have with the rules.
I need to specify that in RP, my character will be ordering this weapon custom for him, for his needs. My goal is having the +2 AC, and still making ranged attacks.
I will be proficient with both a shield and a bow, but the combined item is a new weapon, not specified in my proficiencies... Is it reasonable to think that I can be proficient the combined item? What kind of balance can I expect of this kind of item?