Re: Alcohol in the base?
From time to time I add a bit of peppermint schnapps - gives it that cooling sense and the mint flavor even without mint shisha. I've done the vodka thing too, and it seems to give a slight additional buzz for the first little bit, but it fades quickly. Try the peppermint schnapps though - it's great added flavor.
EDIT: - it doesn't take much - I put probably 2-3 shots worth into the base, but it depends on how much mint you want.