Since I am on a defending spree of the OP tonight... Here goes..
I know each of these stallions personally, as well as the OP and her mare. The mare is NOT underweight. She WAS last winter due to a bad feeding program which has been fixed and the mare has been perfectly fine all year. As on Monday, she is a solid 5 on a BCS. I wouldn't say that is "underweight", at all. As for the OP, she is capable of caring for the mare whether she is in foal or not.
So, firstly, the red studs name is not "Last Chance". Idc what his owner says, OP. Last Chance passed in 1985. His name is "Fast Chance", and if I remember correctly, he is one of only 2 stallions with his particular blood line left in the US. While he himself is not much to look at in the photo, he is built correctly FOR HIS BREED. Also, he has yet failed to produce a foal that was not excellent quality. Every foal of his has been very well gaited, properly conformed, and had a wonderful mind with a good work ethic and trainability.
Secondly, the champagne colt is only a 2 y/o and has only just been bred this year to two "test mares". He had a bit of a rough start before his current owner got him, which is why he is a bit thin. He is startingg his under saddle career now and will be shown and campaigned.
Thirdly, the photos of the cremello tobi stud do NOT do this guy justice! They were also from his long yearling year, and why the OP picked those out of all of his others, I do not know. This stud is a proven, winning show horse at only 3. He also carries super bloodlines. His first foal crop has only just hit the ground, but each one has been nothing but quality.
Fourthly, the black/white stud is a real Walking Horse! Also old pictures. He is my pick out of the lot simply due to the foals he has produced. He is AMAZING in every aspect and his foals are no exception. I rode his very first colt and that guy is a walking, shaking, natural fool with the mind of a 20 y/o and built like a brick house!
Not a single foal from this stallion has been anything less than great.
Now, as for the stud fees. There is absolutely nothing wrong with $250. The pleasure bred side of TWH and SSH are lower than the performance/"big lick" side. This is not uncommon or a sign that these are low quality horses. These studs' owner produces some of the nicest foals around every year. And no, the color is NOT what made them be left studs. The color is just the icing on the cake. But, if you aren't knowledgable in the TWH world, it is quite common for horses of this breed to be "colored" and many are homozygous for this and that. But these horses combine the best of all the qualities of the TWH/SSH. Conformation, trainability, mind, and color LAST. As a good friend of their owner, I can assure you they strive to produce quality offspring and work hard with their horses. They also set their fees low to allow the "common man" to get a breeding to an exceptional stallion at a low price. Money is not the object to them, bettering the breed is.
I'm truely sorry if I sound hostile, but it is only due to frustration at the lack of simply being able to answer the question asked. It is the OP's perogative to breed her mare to whatever she wants and no manner of online "don't do its!" make a large difference. I'm posetive she knows the pros and cons of what she's doing. And she IS trying to find the best match for her mare to produce the best she can.
ANE finally, IMO, OP should cross the mare on the 4th horse. He suits her the best, and he wilproduce a gaited spotted foal WHO WILL BE ELIGABLE TO BE REGISTERED as a NSSH and SSHBEA. NOT a grade foal!
*steps off soapbox for the night*
Tennessee Walking Horses
The "Glide Ride"