Could a blind person with a death note exchange half their life to see again?
From the wording of the rules of deathnote and the way the "eyes of Shinigami" are explained in the anime this scenario seems plausible. 

However, as I've said many times in such questions this is meaningless speculation since either scenario is plausible and the rules of DN leave room for speculation. So other than just saying this scenario is possible and saying that some of our better fanfic writers picking this up as a possible plot point Idk what else to add.

However, to add to the "suspicion" on a blind man scenario. There are many ways this would be a bad idea. 


Suddenly a blind person is cured. Publicity, DN user is exposed. Someone else may have seen them together
It is not so easy to hide that you are not blind. Plenty of involuntary actions, such as dodging, moving hands etc give away the fact you're not blind. It would be much tougher for a blind person who has healed to hide these signs.


So on surface it may seem a good idea, but it has its own pitfalls, pros and cons just as another. Also the blind person will lose his sight the moment he gives up ownership of the DN. I would like to think that the KIRA will kill to get the Notebook back.