@PabloZ couldn't you use themes instead of the skins.
So effectively create two or more themes.
On our new build on 19.2 we will be creating two different themes depending on the two types of customers we have.
Then with some sort of variable you assign a user to a given theme eg if user id is odd show theme X if even show theme Y. You would also need to track the usage by passing custom event data into GA so you see which is better from a holistic point of view (eg product impressions, clicks, conversions etc
@David Durst another option would be to use a A/B testing tool to essentially override to look & feel. We are currently using this method on our current live Elbrus site. We are using the Monetate tool but any A/B testing tool would be fine.
Only consideration would be the slight flicker as the look & feel changes.