No problem with that so long as you observe good sanitation and a reasonably dense concentration of sugar. It wouldn't be my preferred method, but I'll explain it anyway.
Boil a clean mason jar for 10 minutes then keep it submerged in the hot water until you are ready to use it. You don't need to use a two-part canning lid. The white plastic lids sold by Jardin / Ball that are made to fit a canning jar are perfect. Wash the lid in hot soapy water, rinse well, spray some Star San inside, and set on a clean towel to dry.
Mix your solution in a 2 to 1 ratio of sugar to water. Two parts sugar to one part water. This concentration will keep better than a 1 to 1 mix. Bring it to a boil and simmer for 5 minutes, covered. Let cool a bit, then pour into the sterilized mason jar. Cap and refrigerate.
Example: Let's say you normally use 3/4 cup priming sugar for a 5 gallon batch of beer. To make a quadruple batch of thick simple syrup, mix 3 cups of sugar with 1.5 cups water. The final solution will fit in a quart mason jar. It'll last in the refrigerator for months. Use 1/4 of your total volume of solution per 5 gallon batch of beer to ensure you are getting the right amount. You'll need to adjust up or down according to the actual amount of beer you are priming.
You could make a 1:1 solution that will be thinner, but it won't keep as long. I'm not really sure how long it would be good for, but most recipes I've seen say 1:1 simple syrup is good for a month in the fridge. Personally, I've used 1:1 syrup in cocktails that was 9 months old, and it was fine. But I was mixing it with alcohol.
Overall, I'd say the approach you are suggesting is more trouble than it's worth, and you will have a hard time determining the optimum amount of solution to use for priming.
The best way to prime is to calculate the sugar addition by weight based on the
BYO priming table, which considers volume, fermentation conditions, type of sugar you are using, and the volumes of CO2 you want in the finished beer. It really doesn't take that long to make the priming solution each time you go to bottle, so I don't see a big advantage in making it up in advance.