As dogs get older they can begin to have issues with their backs and/or their hips. You may want to consider a pet ramp to make getting in and out easier on your dogs.
For riding with the doors off you can get a pet harness that will keep them restrained just enough to protect them, but still give them enough freedom they don't feel like they are trapped.
The last thing to consider is the hair from the Huskies. You will want some kind of liner that gives the dogs traction, but doesn't hold onto the hair and look bad. Can't help you on that one - you'll have to look around for that one. My sister runs a Husky web page/blog of sorts.
I put the seat down just like you have it and put a dog beg over the crack. Keeps my dogs from getting their legs caught down there and provides them something comfortable for travel. My dogs go pretty much everywhere with me including the trail and it's worked out well so far. Plus, they have the extra room in the back to walk around.