I don't see the thumb safety to be at all difficult. With the 1911 it's a quick sweep that becomes second nature either way. My Tanfoglios allow the safety to be operated at any time as do the CZ's where applicable and others including an FNP I owned. For me the safety is also a natural index point for my strong thumb and is part of my grip. All my guns have external safeties and they all follow the up for safe and down for off convention. A mix might create some confusion in the automatic brain but not for long with a practised shooter. Some don't like the grip safety either. It has never been a problem for me from day one and I wouldn't even consider having it pinned.