Yes, you could do it but to be on the safe side you'd want to pour it into sterilized containers. You'd also be storing a lot of water--kind of takes up a bit of space.
What you can do if you wish: Make a modified simple syrup and store the syrup. Then you need only to measure out the syrup, mix with water and you're good to go.
Assuming for the moment that you use equal parts sugar and salt (whatever ratio is fine) and that you use normally, say, 1/4 cup of salt/quart of water for your brine, you could mix your salt and sugar together in a pot--let's say 2 cups of each--then add an equal amount of water (in this case 4 cups), bring to a boil and stir till completely dissolved. Cool, store ina clean container. 1/2 cup of this syrup added to a quart of water would equal the 1/4 c salt/qt water ratio, but you could make it stronger or weaker, as you wish.