The storage of anything on the back, including sword and shield, is entirely impractical except for traveling.
If anything, I'd like to see a mod that removes back storage entirely.
Actually, a large number of shields in history have a sling attached. This allows you to easily sling it over your shoulder for times you don't need it, and provide easy access to it should you be surprised.
Swords on the back are possible, even practical, but
Drawing swords out of a scabbard strapped to your back is not. At least not for anything much longer than your forearm. Human arms simply aren't long enough. Sure, it can be done, but it isn't easy, it isn't quick, and it is a great way to accidentally slice the back of your neck open.
You are also likely to wear the sword on your
Right hip, not your left. Why? Because it is actually easier to draw the sword from the scabbard in a lot of cases for many fashions. Easier to draw in tight quarters and not accidentally chop a bit of flesh out of a buddy, catch it on your shield as you ward off a blow, etc. The usage switched throughout history, but last I had heard the modern opinion, based on art and re-constructive archeology is that the right hip was favoured more for a longer period of history, and the left hip-cross-draw is really a modern invention for 'small swords/walking swords' and their like. (You don't have a shield to worry about, and your left hand can hold the sword steady, leaving your right hand free for all of its gentlemanly duties.)