Place I worked at one time had a stud that would rip holes in his sides......sort of like the blanket ripping, only he did it to himself. Sad story really. Apparently they got him from somewhere that had kept him in a stall for about 5 yrs of his life. The only time he was taken out was to breed a few mares a year, and then he went right back in his stall. So, he was a bit neurotic, to put it mildly. In any event, they put a neck cradle on him to stop him from reaching his head around to bite himself. I've seen them listed in the catalogues....jeffers, Valley Vet, and I think American Livestock too.
Maybe you can enlighten me, as I'm also not quite sure what his jumping ability has to do with him wearing a blanket or not. I don't know very much about jumpers, but I wouldn't think that wearing a blanket or not would affect his performance. If its the length of his coat you're concerned about, maybe try lights and a heat lamp in his stall to help keep it shorter? Best of luck with him, he sounds like a handful!