From the oystercard.com site

"We are looking at ‘capping’ the maximum amount you will pay in any one
day but have no firm details or a planned introduction date at present."

Given this, do you think it would be a good idea for 1 day travel cards
to be possible on Oyster?

It is rare that I need a 1 day travelcard - it just seems so backwards
to have to go back to a paper ticket.

Tim