As the OP suggested...Aperol to make a Spritz.
I knew it wouldn't be long before HowardLong was along. I remember some of his epic TR's over on V-Flyer back in the day!
Guest ales are a great idea. I am surprised that CAMRA has not approached BA (or BA approach CAMRA) about this- what a great way to promote the excellent smaller breweries we have in the UK.