I think the first issue one will run into when using the rpi, is the network connection. The network gadget on the pi is run thru the usb, and it's not a 'really cabable' network setup, cannot come anywhere near saturating a 100mbit link. That becomes a non issue tho if you are using wifi between the gadgets, because in general wifi is an order of magnitude slower than a wired link, no matter how much they hype various mbit numbers on the box advertising, you wont get that kind of thruput on a wifi link for a lot of technical reasons. This is the reason we ran gigabit out to the back lot where we plan to build the observatory. We will run the autoguiding software over the network, so full thruput capability is important to us. Current plan will likely have the cameras and mounts connected to a little atom based motherboard that has gigabit ethernet connections, so network thruput will not be an issue for us.
Years ago, my wife and I used to do the 'mobile astronomy' a lot, we had a camper van and would travel to star parties regularly, set up everything in remote locations then run it all for a few nights while camped there. Our setup was 'his and hers', consisted of two complete setups. One was an eq6 + c8, the other was an heq5 + 110mm refractor. Both were run from an atom based netbook, which we had bought the large 'extended life' batteries for. We had a 80ah deep cycle battery in the camper van, with an inverter.
Our experience was, we could go all night on a typical July or early August evening with that setup, but as the nights got longer in September, we would reach a point where we had to start the engine on the camper van because the battery would get low enough, the inverter would shut off. That was ok if we were out on our own, but it's forbidden at most of the larger star parties, no generators or vehicle motors running after 9pm. It was very important that we got the battery fully charged thru the day at those events. We usually ran a small generator for a few hours during the day to get the battery fully topped up if we didn't take the van for a drive that day. There were a couple mountain top events we went to every summer, and during the day we would drive down to a lake to go for a swim to cool off and clean up, and the camper van electrical system would do a good job of topping up the battery over that drive (an hour each way). The other trick to getting maximum life out of the battery, was to leave the netbooks plugged in for the first 2 or 3 hours and run them off of our main supply, but unplug them around midnight, then let them run from the internal battery till sunrise. The marketing literature bragged about 12 hour battery life from the big ones we bought, but, our experience was once all the astro stuff was running, they were good for somewhere between 4 and 6 hours, depending on how cold it was out. The colder it got, the less time we would get out of the batteries. Same issue for the deep cycle battery in the van, the colder it got, the less run we would get from it, and when ambient temps were around 0C, it only lasted half as long as running the same kit on a mid summer evening with temps in the 15 to 20C range overnight.