What is the feasibility of dynamically loading the imagery in the future, like google earth does?
As 100mb and even 1000mb internet connections become more common bandwidth isn't really a concern.
Obviously there's some CPU required for processing images
I would actually expect the biggest road-block to be in the form of whatever EULA the FSET/USGS site has on how applications can interface with their website.
The rich-man solution would be to just download all the data and store it in your own AWS account.