Yes, they are suitable for two piggies, but only two females. If you were to get two boys you need a 6ft hutch - boys need more room and would possibly struggle with lack of in a 5ft hutch.
Your hutch also does not need to be a two storey should you not want it to be, or want to save money and get a single storey! Upper levels of hutches don’t count towards the space anyway as piggies are ground roaming and some won’t use ramps.
Absolutely a shed is a great idea, particularly for winter. You will need to keep an eye on things in summer depending on how your summer house behaves. My boys live in a hutch in my shed and its a godsend in winter but gets too hot in summer so they have to come out.
I do have a two storey hutch but I don’t allow my boys to use both levels (the ramp has been removed). They live downstairs and have constant access to the shed floor in summer. In winter they have the downstairs part and shed floor during the day but I lock them in the upstairs part overnight and ensure it is stuffed with hay as it is much easier to keep just the upper level warm enough. Plus it saves on bedding and hay costs to only have to fill one half fully (the amount of hay I get through in winter is crazy!)
