Like others, I am used to checking the nutritional label for the % per 100 grams. However, I assume we will still have that table and so what we need in new labelling is something easy for the people who don't read nutritional labels.
Pictures of teaspoons would be great - especially if they are colour coded for natural and added sugar. (As long as 'natural' is not misused to include added sugar from 'natural' sources such as fruit juice as a sweetener.) But I am torn on whether it should be teaspoons per average serving (again that would be open to abuse with unrealistically small servings) or per 100grams. The problem with the latter is that 100grams may bear no relationship to the amount being consumed (especially if it is a food eaten in much larger amounts) and give false reassurance as to how much sugar is being consumed. On balance I suggest using teaspoons per average serve and keep a close eye on that so that manufactures are called out for using unrealistic serving sizes.
I have never liked the use of % of RDI as we vary so much in our energy use that RDIs are really not accurate for the majority of us. We either need less (if we exercise less than average) or more (if we exercise more than average). How many of us are right on the average?