"...I also thought that, as some people reporting theirs skin to peel off on the beginning of treatment with the PT, but that mostly apply to rosacea treatment with PT soap. Did anyone noticed that?..."
I have never heard about that, nor have I personally experienced this. A soap with a high cleansing value might be the culprit more than the PT. But I don't know everything there is to know about PT, so maybe it has that effect for some people.
"...I think I will go for lavender scent, or lavender and mint, or no scent at all - I need to check how the PT smells of its own..."
If you've never smelled pine tar, then be aware it has the strong odor of burnt rubber or very smoky campfire, depending on the brand and your nose. Added scent needs to play well with that kind of distinct, strong aroma.
That said, if you're making this soap specifically for troubled skin, it may be best to stick with just the PT. Consider the soap to be a medicinal product and choose your ingredients accordingly. Any additives should provide therapeutic benefits that aid the PT to do its job, not just added for the sake of adding them.
It may just be me, but I don't think I'd care for mint in a soap intended for washing the irritated, delicate skin of my face.