The owner of the stllion is on the right track-breeding Tb mares (or crosses) to him refine him, correct a few of his conformational flaws, and bring out a floating movement that is typical of foundation X TB crosses. I have done this cross several times and with the "right" TB conformation to the right foundation conformation have produced some spectacular HUS and hunters.
Your mare is very cute-and wow what a history on her. Glad you've got her issues at hand and are working on them. With her racing background she has the typical stockier "run" look to her which is why you are having such fun barrel racing her-she's built to do that. I just don't think this is the right cross for your mare as typically the TBs used on foundation horses are more refined distance type runners-greyhound body types come to mind.
Because you mare does not have the cutting/quick turning pedigree I would certainly look for stallions with those bloodlines or at least one with a pedigree with proven quality closer up so you have a general idea what you can do with the foal once it is ready to be trained.
Here's one off hand I found in Oregon-I really like him and some very nice foals.
Sun Tan Party Standing at Stud