As SLF regularly using turboprops to / from GCI, I have been in situations where the passengers / cabin crew have alerted the flight deck when ice has been building up on the wings (resulting in a quick drop in altitude) and a (longer) windy approach to GCI. I would guess however that if ice is forming on the visable wings, it's also on the tail. Given that the ATR's/ Q400's on local sectors like LGW-GCI are in ice forming conditions for a longer % of their flight, is it time to access the potential risk for these flights as oppossed to longer flights, and set some min /max values in keeping with current local conditions?