An errata set would be great. I would definitely prefer to have cards the same size, rather than smaller. I would rather pay $2 to get the essential cards replaced.
On the issue of number, would selling blank cards for players to create their own cards be an option? I would definitely purchase blank front cards of the same (or similar) size to be able to design my own cards. Including a batch of blank cards with the replacements would be enticing to me.