wow, it would take a lot of vanilla extract, that would cost a fortune!
I say if you want to do the alcohol extraction, use everclear, evap it down to tar and then reconstitute it with the required amount of vanilla extract. All vanilla extract is is grain alcohol and vanilla absolute anyway, they just jack up the price and sell it in wee bottles.
I think it would be easier to just steep the herb in the cream base along with whatever flavorings - a few vanilla beans thrown in while steeping it would give it incredible dimension to the flavor.