TB/Percheron's (or many other light horse/draft horse crosses) make amazing jumpers
Really sturdy horses, I don't worry about their legs as much as a petite thoroughbred with matchstick legs, ha ha ha.
As far as starting a horse over fences, is there any experienced coaches around that can help with it? Speaking from experience, jumping is something that needs to be taught correctly, horses can get ruined very easily, and have their confidence shaken by and unbalanced rider trying to pop them over fences (not saying this is you by any means, I have just seen it happen on many occasions)
Start VERY VERY VERY slow and low.
Start with trottig poles. These can be placed at various distances depending on the stride of your horse. Anywhere from 4 - 6 feet will allow a horse to trot over them, 4' making the horse trot in a shortened stride, 6' making the horse lengthen its stride. 4.5' - 4.75' allows for a fairly standard length stride. Make sure you can keep the horse straight, balancedand rhythmic over poles before you ask him to go over a fence. Once the horse has been doing this excercise correctly you can add a low (I stress LOW) jump at the end of the line. Just a small cavaletti at the lowest point should do, just getting him to pick his feet up. Do not go high as it is very easy to rattle a horse's confidence by overfacing them too soon.
Here are some good references for starting a young horse over fences. But I can't stress enough how useful an experienced trainer or coach is.
http://www.ansursaddle.com/AskAnneArchi ... tingToJump
this one states the procedure for lunging a horse to start... but I can't see why these steps could not be used under saddle as well. Thse stes are to be taken VERY SLOWLY. Certainly not all in one schooling session!
http://lorienstable.com/articles/jumping/150-the_horse/
Do not take this as the bible, PLEASE. Ha ha ha, everyone has different opinions. Try to, if you cannot get a coach or trainer out, at least consult someone for someone for tips relative to your situation. Also, I cam assuming this is not a very young horse, as starting a very young horse over fences is a whole other can of worms, ha ha ha.
TCFC