I like the Hanoverian and Thoroughbred either on their own or as a cross. If a thoroughbred, however, I prefer one with larger bones rathar than some of the pencil thin versions that are out there..it just makes me wince on the landing every time I see a small boned thoroughbred jump a good sized fence.
Appendix QH who have the QH build, larger bones and stockier, but have the TB height and conformation are also good prosepects. When I got my first horse way back when, another girl had an Appendix. This horse was 16.3 and stocky and could jump the moon and did very well in the then AHSA, or maybe it was AHJA..could never keep the two straight, Amateur Owner Hunter division.