Your mare is gorgeous!
If you can't afford the price tag of a warmblood stud, but want to add some bulk and mellower attitude like those, there are alot of nice, correct quarter horse studs out there. If you look for a background of "foundation" lines, you can get a bigger boned horse when crossed with thrbd mares, just watch for good feet on the stud. And alot of them have refreshingly great attitudes(former thoroughbred convert here). You would also be looking at a prospect more for the equitation and hunter than jumper, as the qhs don't have that springloaded rearend for jumping(just jumping forward) that warmbloods do. But of course, its all generalities-I would just encourage you to determine the physical and mental characteristics you need to complement your lovely mare, and keep an open mind on where you will find those traits-after that its all a krapsshoot! Good Luck