If you use "could" in this sentence, it has basically the same meaning as "might." If you use "would," it seems a little strange. It might be better to replace "might" with "will."

"Would" is past form and the sentence discusses a future event so that is definitely wrong. It even "sounds" completely wrong. "Could" might be a bit more complicated, but I'd say it sounds a bit off too. Will/might are preferable here IMHO.

"I could do it." It's possible that I have done it. "I would do it." I intend to do it, but something is stopping me. "I should do it." It is correct, proper, in the best interest, etc, that I do it. I would make too many mistakes. This implies a contrast, like in the sentence above. "It's likely that I will make too many mistakes." "I wanted to have foreign buyers over, but I was worried I would make too many mistakes."

I don't know much about grammar, but to me, they don't sound right. 'Would' definitely sounds wrong. 'could' is possible, but still doesn't sound right.