Removing travel cards will make business travel a pain in the backside. Right now we can just tick a box when booking a ticket that ends at a London terminus and a travel card is included for that journey from the types available. Or you can just buy them separately by using the zones as departure and destination.
There isn’t a good alternative to allow pay as you go for business travellers. You’ll need a shared oyster (nightmare for finance and a pain for the users), give everyone their own contactless card (massively wasteful for infrequent travellers and lots of overhead costs) or have them use their own card and claim it back on expenses (more overhead and can cause issues when staff don’t want to use their own cards). You still need to book the other tickets too, so all of this just adds more cost.
I support some of our teams when they need to navigate the fun of group ticketing and travel planning and I can’t see this being a nice thing to deal with when trying to shift large numbers of people around London