Haflingers are great sturdy breeds but most of the breeding now of days is done for ''light'' style breed which is really a pity, plus they tend to run on the short side and he's kind of tall to be riding a 14.3hh horse. :)
I'd surely say a Fresian due to their conformation and abilities to carry weight over time.
Percherons are nice but surely run on the tall side!
Belgians would be a good idea. They are shorter as mentioned, but very sturdy.
Suffolk horse is a very beautiful draft, they don't have the feathers like most other drafts and they have a very elegant look with a lot of strength. They are actually really not that common, and kind of expensive but it'd be a worth while investment! 8)
Shire's were not mentioned. They are very nice breeds, similar to the Clydesdale but with slightly different conformation and colors.