How to make hard candy with only fruit as a sweetener
I think classic hard candy would be difficult if not impossible to make with fruit juice because it combines the fruit sugars (fructose) with a lot of other things, and hard candy is normally made by heating sucrose (table sugar, which is 50% fructose, 50% glucose) to the hard-crack stage (300-310F) to the point where it is essentially 99% sugar.  As the sucrose heats it  hydrolyzes into glucose and fructose which changes the structure. 

Pure fructose does not behave the same way as sucrose. I think you need some glucose to get it to form into a hard candy.  (You can also make hard candy from sugar and high fructose corn syrup instead of from table sugar.)

Additionally,  fruit juice isn't pure fructose to begin with and the other things in the juice would cause problems with the process and would probably scorch. 

I think the idea given in the comments of trying for a gummy or a syrup will work better.