Um, can we go back to the question first. I don't think it's an easy task for your iPad to open 1GB+ files without crashing it completely.
In this case it's clear that a tablet is not what you need. Even an Android tablet that allows you to plug in a USB drive won't be able to open those big files. Just use a PC or a Mac.
Case closed
I don't think the file size is the real issue here. Why doesn't Apple allow the user to expand the storage capacity of an iPad, either through a SD slot, or USB port. I know they want to push you in the direction of buying bigger internal storage from them but all they have to do is only make it available in the 64GB ipad. That way, you max out on what they offer on internal storage but have the option of expanding. Win-win.