Hi Susan! I’m afraid I don’t see any way of that working out well. There wouldn’t be any easy way to tell how much lye would be needed to break down the particular oils in the lotion.
You’d also have a lot of additives in the lotion that might react in a weird way with the lye.
Also, you don’t want to use any old ingredients in soap since that will make the finished bars prone to developing DOS (dreaded orange spots – which means the soap has gone rancid.)
I like your train of thought though and have wondered in the past if it’s possible to add a bit of someone’s favorite lotion to enrich a soap (maybe as an add-in after cooking hot process) but have never researched or tried the idea to see if it can be done or not.