What rootstocks would you recommend?

Rootstock choice depends on multiple variables, such as the desired tree size, climate, planting system, etc. Susceptibility to fire blight is sometimes a problem with cider varieties, especially (but not only) in the eastern half of the USA. Fire blight can really devastate an orchard if not properly managed. If you’re worried about fire blight in your area, you might consider Geneva rootstocks, which have been shown to be highly fire blight resistant.