Please read this info about Grey's and Melanomas, My old grey stud has had several melanomas removed (ones they actually affected him, some made it hard for him to poop) While others he still has make it so his mane and tail are falling out. Some are over his eyes and invade on his vision. So you might want to think about whether or not you actually want to deal with that.
Also have you raised a foal before? It's a lot of fun, but also seriously exhausting and frustrating. Are you prepared for an aggressive stud colt if that what you should end up with? If you were to fall on hard times what are your back up plans for your horses? Is there someone else you know who could care for them?
I wonder if maybe you'd be an ideal home for say a Nurse-mare foal. These are mares who are bred at the same time as an expensive show horse (or sometimes mares who die giving birth) when their foals are born the nurse mare's foal is taken away and the given the other mare's foal to raise (so the other mare can go back to competing right away). The other foal is typically sold (bottle fed until they get sold) or just thrown out.
I think if you're up to the battle of raising a foal you may want to look into raising one of those unfortunate souls instead of producing another?
I'm sure you've thought everything through a million times over, but I really do plead with you to look into other ideas, like foal adoptions. :)