It depends on what you want to do with your Dressage. Theoretically, any horse can do a basic level of Dressage. If you want to be competitive and ride at the higher levels, that is where you need to start being more selective about breeds.
I own two hanoverians for Dressage, but also love Oldenburgs and many of the KWPN's.
Basically, warmblood's (true warmbloods, not draft x) are the key player in high level Dressage. Iberian breeds are fairly popular but the Warmbloods really do rule the roost when it comes to competition Dressage, due to their all round ability to collect AND extend their paces to a high degree. Like anything, not ALL warmbloods are going to get you to Grand Prix, but you've got a better chance on a warmblood than a standardbred that is not built for the job.
In Australia we don't have many haffies at all, but from what I've seen on this forum, a few members compete their haffies in Dressage quite successfully. They're not terribly competitive against the warmblood 'purpose bred' breeds, but they seem to hold their own and are a great little horse for a rider wanting to go and have fun, or compete in pony Dressage if applicable.
I'm very short too, with stumpy legs! My 1 year old is only 15.2hh, but pure hanoverian with fully imported bloodlines. The 2 year old will mature around 16-16.1hh and is also by an imported and highly successful Grand Prix Dressage stallion who puts a wonderful stamp on his progeny. Not all warmbloods are huge ;)