I love her and want to give her something, this is not for me nor do I want a another women.
I need an honest answer as we have a very good marriage, am I crazy or if this works will this even enhance our relationship even more.
I understand what you are saying, and you do sound genuine.
But you need first to understand a few things.
1] You are speaking from a position of male insecurity. There are many men with similar problems like you , but they tend to handle it differently. Those who have chosen your path always end in disaster because they were insecure.
You think your marriage is secure , but your insecurity over you ability to fulfil your perception of your wife's psychosexual needs will eventually ruin it.
2]You say you " love her and want to give her something."
She loves you, even if your penis is small. She's married you and has been faithful to you for all of these years. Yes, she loves your penis , and the man attached to it too. She enjoys pleasuring herself, and talking about these fantasies in front of you because she's comfortable with you!
3]For some people sex is just an act. You need to decide for yourself what sex between you and your wife means to you.
You must decide if she is just a toy that you can lend to another man , like the old worn out playboy magazine you and your buddies used to share for fun when you were kids.
If she means more than that to you , then why do you want to share the most intimate aspect , her body with another man?
4] Not all fantasies are meant to be enjoyed in real life. If they were , then obviously they would no longer be fantasy.
Absolutely nothing is wrong with having the fantasy, but it is way too risky to make it reality.
You cannot control the consequences. Its like playing Russian Roulette, very thrilling and exciting, but you never know when the bullet would come flying out of the chamber , and in a flash , your life would be gone.