Using an adventure touring tyre for off-road fun

Hi all. I've been mulling over how best to get the most out of my Croix de Fer commuter next summer by taking it off road for some bridle-path bashing and hopefully a bit of flowing singletrack. I commute from Sutton to the City (14 miles) 5 days a week. I guess I am only a few miles from dirt in the Surrey hills.

To illustrate my thinking, here is a chronological summary of my musings:

1. Lusting over the Monstour thread and dreaming of 650b fat tyre wheelsets.
   
2. Realising how expensive said wheelset, tyres, casette and disk rotors would be.
   
3. Thinking about cyclocross tyres instead.
   
4. Imagining the faff of changing tyres every Friday evening before a weekend ride and again to put the commuter tyres back on before Monday.
   
5. Wondering if I could get away with a fat, durable semi-slick on my bike that might be fast enough for my commute and give me sufficient grip for dry singletrack. I'd never off-road in mud as my bike lives inside, so I'd have to get it very clean and dry after every ride.
   
   

What do you knowledgeable people think? Could I commute on something like this and not be cursing its width and weight? Would I see any benefit on hardpack compared to just braving it on my 28c Conti Gatorskins? If you have a different "do-it-all" solution I'd be interested to hear how that works for you.