You and me both - I have a southfacing balcony too. Almost anything that will grow in a pot which doesn't require shade will grow there - the problem is, plants get bigger, and run out of root room in their pots, and that might be the trouble with your aubretia, because this plant does like full sun.

Grasses are okay, but don't forget many of them disappear completely in winter - a much better bet are things like Phormium, which are evergreen and do wave in the breeze, but you will need deeper pots for those, I grow mine in 18 inch high galvanized tomato pots. Every 2 or 3 years, I turn them out, cut them in half and replace one half in the container with some fresh compost. Smaller Phormiums like Platt's Black and Cream Delight are the ones to look for, although they never get overly large being in containers anyway.

A smaller grasslike plant to check out, which remains evergreen, is Ophiopogon nigrescens, does well in those conditions, doesn't need a deep or large pot, but again will need splitting once it gets too big.

Even Clematis do fine out there, regardless of being in baking hot sun, though I do try to keep those pots behind others to provide a bit of shade to the roots. One to a 2 feet deep x 12 inches wide pot; eventually they get too big and have to be split or discarded. During hot, sunny weather, even the clematis need a good soak every day.

Another plant which does well in these conditions is Calllistemon citrinus - lovely when in flower, but gets moved to the side once it's flowers are done, though it is evergreen.

For summer planting, Pelargonium geraniums do very well indeed in these situations - I have an ivy leaved climbing variety in a 2 foot deep tub that's been there for 4 years - the previous one was there for 10 years and was 5 feet high, but then we had that really severe winter...