I hadn't considered the 'ankle room' issue. The traffic cone looks kind of hokey, but like Nat's suggestion perhaps a plumbing funnel could be used. As far as the dump hopper goes, it sounds like a BIG mess! I'm contemplating just leaving the waste in the drum! Sturdy plastic 55 gallon drums are about $10 each on craigslist, and at that price I could afford to let them compost right in the barrels, and never have to mess with the stuff until it's pretty much potting soil.
I agree about the 'responsible' bit. I plan on making sure I see the waste through until it is safe to spread. I will be storing it on my parents farm (likely in the 'original' drums) and then eventually on our own piece of land a few years down the road. The plastic bag bit would work for me but I don't expect my wife would like it!
Also, I'd like a wood stove, but I don't plan on burning it in the summertime!
That's another reason to go with bigger drums-- to make sure we can boondock for at least a couple months at a time without coming home to dump. Water, electricity, food and fuel are easy to find but our current plans don't include too many campgrounds where we'd find dump stations.
What kind of toilet are you running these days?