Are you afraid that you will fall in love with the friend? You have equated intimate contact with emotional attachment so that maybe this is your fear. Regardless of the answer to that question, if you don't want to do it, then don't, it won't help.
Is your wife afraid that she is not being fair to you because she is incapable of the intimacy now? Maybe that is the reason she thinks it's a good idea. Either way, it is very obvious there is a lot of love there.
There are lots of ways to show intimate emotional affections. Cuddling close, brushing her hair for her, a gentle kiss anywhere, a stroking of the cheek, millions of ways to say 'Ilove you'. I don't think that is the issue. I think you are both having the discussions that lead to a decision of polyamory. She seems to be worried about your needs and you seem to be rolling it around in your head whether you even want to take the chance you might develop feelings for this other person....or you may simply not be into this other person.
In my opinion, you and your wife are in the early stages of this growing conversation. Be open and honest. Say exactly to one another what you feel and mean. Don't censor your feelings or words. Talk about what each of you expect should you go through with it and discuss this with the other woman as well. Don't only discuss what the immediate results might be, but also the long term. Would it happen a second time? What if it's still happening in the years to come? What if its a disaster? Would you still all be friends? There is lots to consider. I think the most important questions are gonna be between you and your wife right now.