In the past I've made coconut macaroons with maize cornflour instead of flour for a coeliac friend, and they were a huge hit. It wouldn't be too hard to substitute Splenda or something for the sugar as well.
Splenda works to a point in meringue and pavlova recipes - slight change to the texture and colour of the end product. Finding something to dress a pav would be the problem with the dairy free.
I make a sugar and dairy free fruit cake (yes, I know, the dreaded fruit cake, but they're popular here) every year, it should be possible to substitute gluten free flour for the cake. There may be texture changes, but the original cake is more like a dense slice than cake anyway. Soak 2lb mixed fruit in 2 cups apple juice overnight, fold in 2 cups flour and 1tsp mixed spice, bake in lined tin in a moderate oven ~2 hours or till cooked through.